WorldWideScience

Sample records for modeling regional seismic

  1. A model of characteristic earthquakes and its implications for regional seismicity

    DEFF Research Database (Denmark)

    López-Ruiz, R.; Vázquez-Prada, M.; Pacheco, A.F.

    2004-01-01

    Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size-frequency relationship, the Gutenberg-Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from...... active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez-Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show...... that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non-characteristic events triggered in the faults...

  2. Amplitude Analysis and Modeling of Regional Phases in PNE Profiles in Northern Eurasia and Seismic Regionalization

    National Research Council Canada - National Science Library

    Morozov, Igor B; Li, Hongyan; Morozova, Elena; Duenow, Joel; Zheng, Haishan; Smithson, Scott B

    2006-01-01

    ... is necessary to use regional phases for nuclear test monitoring. Over the past decades, Russian scientists acquired a network of dense, linear, long range, three-component Deep Seismic Sounding (DSS...

  3. Nonlinear time series modeling and forecasting the seismic data of the Hindu Kush region

    Science.gov (United States)

    Khan, Muhammad Yousaf; Mittnik, Stefan

    2018-01-01

    In this study, we extended the application of linear and nonlinear time models in the field of earthquake seismology and examined the out-of-sample forecast accuracy of linear Autoregressive (AR), Autoregressive Conditional Duration (ACD), Self-Exciting Threshold Autoregressive (SETAR), Threshold Autoregressive (TAR), Logistic Smooth Transition Autoregressive (LSTAR), Additive Autoregressive (AAR), and Artificial Neural Network (ANN) models for seismic data of the Hindu Kush region. We also extended the previous studies by using Vector Autoregressive (VAR) and Threshold Vector Autoregressive (TVAR) models and compared their forecasting accuracy with linear AR model. Unlike previous studies that typically consider the threshold model specifications by using internal threshold variable, we specified these models with external transition variables and compared their out-of-sample forecasting performance with the linear benchmark AR model. The modeling results show that time series models used in the present study are capable of capturing the dynamic structure present in the seismic data. The point forecast results indicate that the AR model generally outperforms the nonlinear models. However, in some cases, threshold models with external threshold variables specification produce more accurate forecasts, indicating that specification of threshold time series models is of crucial importance. For raw seismic data, the ACD model does not show an improved out-of-sample forecasting performance over the linear AR model. The results indicate that the AR model is the best forecasting device to model and forecast the raw seismic data of the Hindu Kush region.

  4. Modeling Regional Seismic Waves from Underground Nuclear Explosion

    Science.gov (United States)

    1989-05-15

    source outside the basin, small solid box beneath Ama. Little waveform distortion is observed along the path towsrds Pasadena (upper four trames) while...effects not accounted for in the wed and analytical solutions were derived for soluble interpretations given (Nuttli 1973, 1978, 1981; Herman & special...in a trnition region of COUPLING lengh L. The hybrid method used in the present study allows the the layering. Several types of solutions for models

  5. A transparent and data-driven global tectonic regionalization model for seismic hazard assessment

    Science.gov (United States)

    Chen, Yen-Shin; Weatherill, Graeme; Pagani, Marco; Cotton, Fabrice

    2018-05-01

    A key concept that is common to many assumptions inherent within seismic hazard assessment is that of tectonic similarity. This recognizes that certain regions of the globe may display similar geophysical characteristics, such as in the attenuation of seismic waves, the magnitude scaling properties of seismogenic sources or the seismic coupling of the lithosphere. Previous attempts at tectonic regionalization, particularly within a seismic hazard assessment context, have often been based on expert judgements; in most of these cases, the process for delineating tectonic regions is neither reproducible nor consistent from location to location. In this work, the regionalization process is implemented in a scheme that is reproducible, comprehensible from a geophysical rationale, and revisable when new relevant data are published. A spatial classification-scheme is developed based on fuzzy logic, enabling the quantification of concepts that are approximate rather than precise. Using the proposed methodology, we obtain a transparent and data-driven global tectonic regionalization model for seismic hazard applications as well as the subjective probabilities (e.g. degree of being active/degree of being cratonic) that indicate the degree to which a site belongs in a tectonic category.

  6. Three-dimensional crustal model of the Moravo-Silesian region obtained by seismic tomography

    Czech Academy of Sciences Publication Activity Database

    Růžek, Bohuslav; Holub, Karel; Rušajová, Jana

    2011-01-01

    Roč. 55, č. 1 (2011), s. 87-107 ISSN 0039-3169 R&D Projects: GA AV ČR IAA200120701; GA MŽP SB/630/3/02; GA ČR GA205/03/0999 Institutional research plan: CEZ:AV0Z30120515; CEZ:AV0Z30860518 Keywords : seismic tomography * 3D seismic velocity model * Moravo-Silesian region Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.700, year: 2011

  7. Recent Vs. Historical Seismicity Analysis For Banat Seismic Region (Western Part Of Romania)

    OpenAIRE

    Oros Eugen; Diaconescu Mihai

    2015-01-01

    The present day seismic activity from a region reflects the active tectonics and can confirm the seismic potential of the seismogenic sources as they are modelled using the historical seismicity. This paper makes a comparative analysis of the last decade seismicity recorded in the Banat Seismic Region (western part of Romania) and the historical seismicity of the region (Mw≥4.0). Four significant earthquake sequences have been recently localized in the region, three of them nearby the city of...

  8. REGIONAL SEISMIC AMPLITUDE MODELING AND TOMOGRAPHY FOR EARTHQUAKE-EXPLOSION DISCRIMINATION

    Energy Technology Data Exchange (ETDEWEB)

    Walter, W R; Pasyanos, M E; Matzel, E; Gok, R; Sweeney, J; Ford, S R; Rodgers, A J

    2008-07-08

    We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S in a variety of frequency bands. Empirically we demonstrate that such ratios separate explosions from earthquakes using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world (e.g. Nevada, Novaya Zemlya, Semipalatinsk, Lop Nor, India, Pakistan, and North Korea). We are also examining if there is any relationship between the observed P/S and the point source variability revealed by longer period full waveform modeling (e. g. Ford et al 2008). For example, regional waveform modeling shows strong tectonic release from the May 1998 India test, in contrast with very little tectonic release in the October 2006 North Korea test, but the P/S discrimination behavior appears similar in both events using the limited regional data available. While regional amplitude ratios such as P/S can separate events in close proximity, it is also empirically well known that path effects can greatly distort observed amplitudes and make earthquakes appear very explosion-like. Previously we have shown that the MDAC (Magnitude Distance Amplitude Correction, Walter and Taylor, 2001) technique can account for simple 1-D attenuation and geometrical spreading corrections, as well as magnitude and site effects. However in some regions 1-D path corrections are a poor approximation and we need to develop 2-D path corrections. Here we demonstrate a new 2-D attenuation tomography technique using the MDAC earthquake source model applied to a set of events and stations in both the Middle East and the Yellow Sea Korean Peninsula regions. We believe this new 2-D MDAC tomography has the potential to greatly improve earthquake-explosion discrimination, particularly in tectonically complex regions such as the Middle East. Monitoring the world for potential nuclear explosions requires characterizing seismic

  9. Regional Seismic Threshold Monitoring

    National Research Council Canada - National Science Library

    Kvaerna, Tormod

    2006-01-01

    ... model to be used for predicting the travel times of regional phases. We have applied these attenuation relations to develop and assess a regional threshold monitoring scheme for selected subregions of the European Arctic...

  10. LLNL's Regional Seismic Discrimination Research

    International Nuclear Information System (INIS)

    Hanley, W; Mayeda, K; Myers, S; Pasyanos, M; Rodgers, A; Sicherman, A; Walter, W

    1999-01-01

    As part of the Department of Energy's research and development effort to improve the monitoring capability of the planned Comprehensive Nuclear-Test-Ban Treaty international monitoring system, Lawrence Livermore Laboratory (LLNL) is testing and calibrating regional seismic discrimination algorithms in the Middle East, North Africa and Western Former Soviet Union. The calibration process consists of a number of steps: (1) populating the database with independently identified regional events; (2) developing regional boundaries and pre-identifying severe regional phase blockage zones; (3) measuring and calibrating coda based magnitude scales; (4a) measuring regional amplitudes and making magnitude and distance amplitude corrections (MDAC); (4b) applying the DOE modified kriging methodology to MDAC results using the regionalized background model; (5) determining the thresholds of detectability of regional phases as a function of phase type and frequency; (6) evaluating regional phase discriminant performance both singly and in combination; (7) combining steps 1-6 to create a calibrated discrimination surface for each stations; (8) assessing progress and iterating. We have now developed this calibration procedure to the point where it is fairly straightforward to apply earthquake-explosion discrimination in regions with ample empirical data. Several of the steps outlined above are discussed in greater detail in other DOE papers in this volume or in recent publications. Here we emphasize the results of the above process: station correction surfaces and their improvement to discrimination results compared with simpler calibration methods. Some of the outstanding discrimination research issues involve cases in which there is little or no empirical data. For example in many cases there is no regional nuclear explosion data at IMS stations or nearby surrogates. We have taken two approaches to this problem, first finding and using mining explosion data when available, and

  11. Complex researches on substantiation of construction and seismic stability of large dams in seismic region

    International Nuclear Information System (INIS)

    Negmatullaev, S.Kh.; Yasunov, P.A.

    2001-01-01

    This article is devoted to complex researches on substantiation of construction and seismic stability of large dams (Nurec hydroelectric power station) in seismic region. Geological, seismological, model, and engineering investigations are discussed in this work. At construction of Nurec hydroelectric power station the rich experience is accumulated. This experience can be used in analogous seismically active regions at construction similar hydroelectric power stations.

  12. Southern Appalachian Regional Seismic Network

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M. [Memphis State Univ., TN (United States). Center for Earthquake Research and Information

    1994-08-01

    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.

  13. Southern Appalachian Regional Seismic Network

    International Nuclear Information System (INIS)

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M.

    1994-08-01

    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern

  14. Recent Vs. Historical Seismicity Analysis For Banat Seismic Region (Western Part Of Romania

    Directory of Open Access Journals (Sweden)

    Oros Eugen

    2015-03-01

    Full Text Available The present day seismic activity from a region reflects the active tectonics and can confirm the seismic potential of the seismogenic sources as they are modelled using the historical seismicity. This paper makes a comparative analysis of the last decade seismicity recorded in the Banat Seismic Region (western part of Romania and the historical seismicity of the region (Mw≥4.0. Four significant earthquake sequences have been recently localized in the region, three of them nearby the city of Timisoara (January 2012 and March 2013 and the fourth within Hateg Basin, South Carpathians (October 2013. These sequences occurred within the epicentral areas of some strong historical earthquakes (Mw≥5.0. The main events had some macroseismic effects on people up to some few kilometers from the epicenters. Our results update the Romanian earthquakes catalogue and bring new information along the local seismic hazard sources models and seismotectonics.

  15. Input for seismic hazard assessment using Vrancea seismic source region

    International Nuclear Information System (INIS)

    Ivan, Iren-Adelina; Enescu, B.D.; Pantea, A.

    1998-01-01

    We use an extended and combined data base including historical and modern, qualitative and quantitative data, i.e., more than 25 events during the period 1790 - 1990 with epicentral/maximum intensities ranging from X to V degree (MSK scale), the variation interval of isoseismal curves ranging from IX th to III rd degree. The data set was analysed using both the sum phasor techniques of Ridelek and Sacks (1984) for different magnitudes and depth intervals and the Stepp's method. For the assessment of seismic hazard we need a pattern of seismic source regions including an estimation for the maximum expected magnitude and the return period for the studied regions. Another necessary step in seismic hazard assessment is to develop attenuation relationships specific to a seismogenic zone, particularly to sub-crustal earthquakes of Vrancea region. The conceptual frame involves the use of appropriate decay models and consideration of the randomness in the attenuation, taking into account the azimuthal variation of the isoseist shapes. (authors)

  16. Developing and Validating Path-Dependent Uncertainty Estimates for use with the Regional Seismic Travel Time (RSTT) Model

    Science.gov (United States)

    Begnaud, M. L.; Anderson, D. N.; Phillips, W. S.; Myers, S. C.; Ballard, S.

    2016-12-01

    The Regional Seismic Travel Time (RSTT) tomography model has been developed to improve travel time predictions for regional phases (Pn, Sn, Pg, Lg) in order to increase seismic location accuracy, especially for explosion monitoring. The RSTT model is specifically designed to exploit regional phases for location, especially when combined with teleseismic arrivals. The latest RSTT model (version 201404um) has been released (http://www.sandia.gov/rstt). Travel time uncertainty estimates for RSTT are determined using one-dimensional (1D), distance-dependent error models, that have the benefit of being very fast to use in standard location algorithms, but do not account for path-dependent variations in error, and structural inadequacy of the RSTTT model (e.g., model error). Although global in extent, the RSTT tomography model is only defined in areas where data exist. A simple 1D error model does not accurately model areas where RSTT has not been calibrated. We are developing and validating a new error model for RSTT phase arrivals by mathematically deriving this multivariate model directly from a unified model of RSTT embedded into a statistical random effects model that captures distance, path and model error effects. An initial method developed is a two-dimensional path-distributed method using residuals. The goals for any RSTT uncertainty method are for it to be both readily useful for the standard RSTT user as well as improve travel time uncertainty estimates for location. We have successfully tested using the new error model for Pn phases and will demonstrate the method and validation of the error model for Sn, Pg, and Lg phases.

  17. Improvement of IDC/CTBTO Event Locations in Latin America and the Caribbean Using a Regional Seismic Travel Time Model

    Science.gov (United States)

    Given, J. W.; Guendel, F.

    2013-05-01

    The International Data Centre is a vital element of the Comprehensive Test Ban Treaty (CTBT) verification mechanism. The fundamental mission of the International Data Centre (IDC) is to collect, process, and analyze monitoring data and to present results as event bulletins to Member States. For the IDC and in particular for waveform technologies, a key measure of the quality of its products is the accuracy by which every detected event is located. Accurate event location is crucial for purposes of an On Site Inspection (OSI), which would confirm the conduct of a nuclear test. Thus it is important for the IDC monitoring and data analysis to adopt new processing algorithms that improve the accuracy of event location. Among them the development of new algorithms to compute regional seismic travel times through 3-dimensional models have greatly increased IDC's location precision, the reduction of computational time, allowing forward and inverse modeling of large data sets. One of these algorithms has been the Regional Seismic Travel Time model (RSTT) of Myers et al., (2011). The RSTT model is nominally a global model; however, it currently covers only North America and Eurasia in sufficient detail. It is the intention CTBTO's Provisional Technical Secretariat and the IDC to extend the RSTT model to other regions of the earth, e.g. Latin America-Caribbean, Africa and Asia. This is particularly important for the IDC location procedure, as there are regions of the earth for which crustal models are not well constrained. For this purpose IDC has launched a RSTT initiative. In May 2012, a technical meeting was held in Vienna under the auspices of the CTBTO. The purpose of this meeting was to invite National Data Centre experts as well as network operators from Africa, Europe, the Middle East, Asia, Australia, Latin and North America to discuss the context under which a project to extend the RSTT model would be implemented. A total of 41 participants from 32 Member States

  18. Building a risk-targeted regional seismic hazard model for South-East Asia

    Science.gov (United States)

    Woessner, J.; Nyst, M.; Seyhan, E.

    2015-12-01

    The last decade has tragically shown the social and economic vulnerability of countries in South-East Asia to earthquake hazard and risk. While many disaster mitigation programs and initiatives to improve societal earthquake resilience are under way with the focus on saving lives and livelihoods, the risk management sector is challenged to develop appropriate models to cope with the economic consequences and impact on the insurance business. We present the source model and ground motions model components suitable for a South-East Asia earthquake risk model covering Indonesia, Malaysia, the Philippines and Indochine countries. The source model builds upon refined modelling approaches to characterize 1) seismic activity from geologic and geodetic data on crustal faults and 2) along the interface of subduction zones and within the slabs and 3) earthquakes not occurring on mapped fault structures. We elaborate on building a self-consistent rate model for the hazardous crustal fault systems (e.g. Sumatra fault zone, Philippine fault zone) as well as the subduction zones, showcase some characteristics and sensitivities due to existing uncertainties in the rate and hazard space using a well selected suite of ground motion prediction equations. Finally, we analyze the source model by quantifying the contribution by source type (e.g., subduction zone, crustal fault) to typical risk metrics (e.g.,return period losses, average annual loss) and reviewing their relative impact on various lines of businesses.

  19. Northeastern Brazilian margin: Regional tectonic evolution based on integrated analysis of seismic reflection and potential field data and modelling

    Science.gov (United States)

    Blaich, Olav A.; Tsikalas, Filippos; Faleide, Jan Inge

    2008-10-01

    Integration of regional seismic reflection and potential field data along the northeastern Brazilian margin, complemented by crustal-scale gravity modelling, is used to reveal and illustrate onshore-offshore crustal structure correlation, the character of the continent-ocean boundary, and the relationship of crustal structure to regional variation of potential field anomalies. The study reveals distinct along-margin structural and magmatic changes that are spatially related to a number of conjugate Brazil-West Africa transfer systems, governing the margin segmentation and evolution. Several conceptual tectonic models are invoked to explain the structural evolution of the different margin segments in a conjugate margin context. Furthermore, the constructed transects, the observed and modelled Moho relief, and the potential field anomalies indicate that the Recôncavo, Tucano and Jatobá rift system may reflect a polyphase deformation rifting-mode associated with a complex time-dependent thermal structure of the lithosphere. The constructed transects and available seismic reflection profiles, indicate that the northern part of the study area lacks major breakup-related magmatic activity, suggesting a rifted non-volcanic margin affinity. In contrast, the southern part of the study area is characterized by abrupt crustal thinning and evidence for breakup magmatic activity, suggesting that this region evolved, partially, with a rifted volcanic margin affinity and character.

  20. Reducing Systematic Errors for Seismic Event Locations Using a Model Incorporating Anisotropic Regional Structures

    National Research Council Canada - National Science Library

    Smith, Gideon P; Wiens, Douglas A

    2006-01-01

    ...) to predict travel times of P-wave propagation at distances of 2 - 14 degrees. At such distances, the phase Pn is in the seismic phase that is most frequently reported and that thus controls the location accuracy...

  1. Regional Seismic Amplitude Modeling and Tomography for Earthquake-Explosion Discrimination

    Science.gov (United States)

    Walter, W. R.; Pasyanos, M. E.; Matzel, E.; Gok, R.; Sweeney, J.; Ford, S. R.; Rodgers, A. J.

    2008-12-01

    Empirically explosions have been discriminated from natural earthquakes using regional amplitude ratio techniques such as P/S in a variety of frequency bands. We demonstrate that such ratios discriminate nuclear tests from earthquakes using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world (e.g. Nevada, Novaya Zemlya, Semipalatinsk, Lop Nor, India, Pakistan, and North Korea). We are examining if there is any relationship between the observed P/S and the point source variability revealed by longer period full waveform modeling. For example, regional waveform modeling shows strong tectonic release from the May 1998 India test, in contrast with very little tectonic release in the October 2006 North Korea test, but the P/S discrimination behavior appears similar in both events using the limited regional data available. While regional amplitude ratios such as P/S can separate events in close proximity, it is also empirically well known that path effects can greatly distort observed amplitudes and make earthquakes appear very explosion-like. Previously we have shown that the MDAC (Magnitude Distance Amplitude Correction, Walter and Taylor, 2001) technique can account for simple 1-D attenuation and geometrical spreading corrections, as well as magnitude and site effects. However in some regions 1-D path corrections are a poor approximation and we need to develop 2-D path corrections. Here we demonstrate a new 2-D attenuation tomography technique using the MDAC earthquake source model applied to a set of events and stations in both the Middle East and the Yellow Sea Korean Peninsula regions. We believe this new 2-D MDAC tomography has the potential to greatly improve earthquake-explosion discrimination, particularly in tectonically complex regions such as the Middle East.

  2. Three-dimensional seismic velocity model of theWest Bohemia/Vogtland seismoactive region

    Czech Academy of Sciences Publication Activity Database

    Růžek, Bohuslav; Horálek, Josef

    2013-01-01

    Roč. 195, č. 2 (2013), s. 1251-1266 ISSN 0956-540X R&D Projects: GA ČR GAP210/12/2336; GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : controlled source seismology * body waves * seismic tomography * crustal structure Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.724, year: 2013

  3. Regional three-dimensional seismic velocity model of the crust and uppermost mantle of northern California

    Science.gov (United States)

    Thurber, C.; Zhang, H.; Brocher, T.; Langenheim, V.

    2009-01-01

    We present a three-dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional-scale double-difference tomography algorithm that incorporates a finite-difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled-source explosions, recorded at network and/or temporary stations, were inverted for Vp on a 3D grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km. Our model provides an unprecedented, comprehensive view of the regional-scale structure of northern California, putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features, especially in the middle and lower crust, that have never before been reported. Examples of the former include the complex subducting Gorda slab, a steep, deeply penetrating fault beneath the Sacramento River Delta, crustal low-velocity zones beneath Geysers-Clear Lake and Long Valley, and the high-velocity ophiolite body underlying the Great Valley. Examples of the latter include mid-crustal low-velocity zones beneath Mount Shasta and north of Lake Tahoe. Copyright 2009 by the American Geophysical Union.

  4. Seismic modelling of shallow coalfields

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, D.C. (University of Calgary, Calgary, Alberta (Canada). Dept. of Geology and Geophysics.)

    1987-01-01

    This study was undertaken in order to determine whether reflection seismic surveys can be used to map stratigraphic and structural detail of shallow Plains-type coal deposits. Two coalfields in central Alberta were used to examine and determine optimum acquisition parameters for reflection seismic surveys in such settings. The study was based on 1-D and 2-D numerical seismic modelling using sonic and density well logs to formulate a layered earth model. Additional objectives were to interpret the reflection seismic data in terms of geologic features in the study area, and to investigate the relationship between vertical resolution and field acquisition geometry. 27 refs., 41 figs.

  5. Modeling Regional Seismic Waves

    Science.gov (United States)

    1992-06-29

    the computation of the Green’s functions is rather time comsuming . they arc Computed for each of the fundamental faults, at I1(H) km intervals from 21...this record was very, small. Station GEO displays similar behavior in that the overall features of the waveform are matched, but fit in detail is not

  6. An Investigation of Seismicity for the West Sumatra Region Indonesia

    Science.gov (United States)

    Syafriani, S.

    2018-04-01

    The purpose of this research was to investigate the seismicity of the West Sumatra region in the coordinates area of 94° E – 104° E and 2° N - 4° S. Guttenberg-Richer magnitude-frequency relation and seismic risk have been computed. Historical data of earthquakes used from year of 1970 to 2017 with magnitude higher than 4. The study area was divided into 8 sub-regions based on seismotectonic characteristics, plate tectonic and geological models. The determination of seismotectonic characteristics was based on the level of seismic activity in a region (a value) and rock stress condition (b value). High a value was associated with high seismic activity, whereas high b values were associated with low stress rock conditions, and vice versa. Based on the calculation results, a and b values were obtained in the interval of 5.5-11.3 and 0.7-2. The highest b value was obtained in the sub region 5 (Nias islands), while the lowest b value was obtained in sub region 7 (the Mentawai islands). The sub region 7, Mentawai Islands was indicated as the seismic risk potential areas.

  7. Seismic source characterization for the 2014 update of the U.S. National Seismic Hazard Model

    Science.gov (United States)

    Moschetti, Morgan P.; Powers, Peter; Petersen, Mark D.; Boyd, Oliver; Chen, Rui; Field, Edward H.; Frankel, Arthur; Haller, Kathleen; Harmsen, Stephen; Mueller, Charles S.; Wheeler, Russell; Zeng, Yuehua

    2015-01-01

    We present the updated seismic source characterization (SSC) for the 2014 update of the National Seismic Hazard Model (NSHM) for the conterminous United States. Construction of the seismic source models employs the methodology that was developed for the 1996 NSHM but includes new and updated data, data types, source models, and source parameters that reflect the current state of knowledge of earthquake occurrence and state of practice for seismic hazard analyses. We review the SSC parameterization and describe the methods used to estimate earthquake rates, magnitudes, locations, and geometries for all seismic source models, with an emphasis on new source model components. We highlight the effects that two new model components—incorporation of slip rates from combined geodetic-geologic inversions and the incorporation of adaptively smoothed seismicity models—have on probabilistic ground motions, because these sources span multiple regions of the conterminous United States and provide important additional epistemic uncertainty for the 2014 NSHM.

  8. Seismic hazard assessment of the Hanford region, Eastern Washington State

    International Nuclear Information System (INIS)

    Youngs, R.R.; Coppersmith, K.J.; Power, M.S.; Swan, F.H. III

    1985-01-01

    A probabilistic seismic hazard assessment was made for a site within the Hanford region of eastern Washington state, which is characterized as an intraplate region having a relatively low rate of seismic activity. Probabilistic procedures, such as logic trees, were utilized to account for the uncertainties in identifying and characterizing the potential seismic sources in the region. Logic trees provide a convenient, flexible means of assessing the values and relative likelihoods of input parameters to the hazard model that may be dependent upon each other. Uncertainties accounted for in this way include the tectonic model, segmentation, capability, fault geometry, maximum earthquake magnitude, and earthquake recurrence rate. The computed hazard results are expressed as a distribution from which confidence levels are assessed. Analysis of the results show the contributions to the total hazard from various seismic sources and due to various earthquake magnitudes. In addition, the contributions of uncertainties in the various source parameters to the uncertainty in the computed hazard are assessed. For this study, the major contribution to uncertainty in the computed hazard are due to uncertainties in the applicable tectonic model and the earthquake recurrence rate. This analysis serves to illustrate some of the probabilistic tools that are available for conducting seismic hazard assessments and for analyzing the results of these studies. 5 references, 7 figures

  9. The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard

    Science.gov (United States)

    Malagnini, Luca; Herrmann, Robert B.; Munafò, Irene; Buttinelli, Mauro; Anselmi, Mario; Akinci, Aybige; Boschi, E.

    2012-10-01

    Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate-sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to understand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc, is consistent with geophysical observations and the local geology. In the 0.02-0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earthquakes (5.6 ≥ MW ≥ 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long-duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re-evaluated.

  10. Source-Type Identification Analysis Using Regional Seismic Moment Tensors

    Science.gov (United States)

    Chiang, A.; Dreger, D. S.; Ford, S. R.; Walter, W. R.

    2012-12-01

    Waveform inversion to determine the seismic moment tensor is a standard approach in determining the source mechanism of natural and manmade seismicity, and may be used to identify, or discriminate different types of seismic sources. The successful applications of the regional moment tensor method at the Nevada Test Site (NTS) and the 2006 and 2009 North Korean nuclear tests (Ford et al., 2009a, 2009b, 2010) show that the method is robust and capable for source-type discrimination at regional distances. The well-separated populations of explosions, earthquakes and collapses on a Hudson et al., (1989) source-type diagram enables source-type discrimination; however the question remains whether or not the separation of events is universal in other regions, where we have limited station coverage and knowledge of Earth structure. Ford et al., (2012) have shown that combining regional waveform data and P-wave first motions removes the CLVD-isotropic tradeoff and uniquely discriminating the 2009 North Korean test as an explosion. Therefore, including additional constraints from regional and teleseismic P-wave first motions enables source-type discrimination at regions with limited station coverage. We present moment tensor analysis of earthquakes and explosions (M6) from Lop Nor and Semipalatinsk test sites for station paths crossing Kazakhstan and Western China. We also present analyses of smaller events from industrial sites. In these sparse coverage situations we combine regional long-period waveforms, and high-frequency P-wave polarity from the same stations, as well as from teleseismic arrays to constrain the source type. Discrimination capability with respect to velocity model and station coverage is examined, and additionally we investigate the velocity model dependence of vanishing free-surface traction effects on seismic moment tensor inversion of shallow sources and recovery of explosive scalar moment. Our synthetic data tests indicate that biases in scalar

  11. Recent achievements of the neo-deterministic seismic hazard assessment in the CEI region

    International Nuclear Information System (INIS)

    Panza, G.F.; Vaccari, F.; Kouteva, M.

    2008-03-01

    A review of the recent achievements of the innovative neo-deterministic approach for seismic hazard assessment through realistic earthquake scenarios has been performed. The procedure provides strong ground motion parameters for the purpose of earthquake engineering, based on the deterministic seismic wave propagation modelling at different scales - regional, national and metropolitan. The main advantage of this neo-deterministic procedure is the simultaneous treatment of the contribution of the earthquake source and seismic wave propagation media to the strong motion at the target site/region, as required by basic physical principles. The neo-deterministic seismic microzonation procedure has been successfully applied to numerous metropolitan areas all over the world in the framework of several international projects. In this study some examples focused on CEI region concerning both regional seismic hazard assessment and seismic microzonation of the selected metropolitan areas are shown. (author)

  12. Modeling, Analysis, and Preservation Techniques for Historic Reinforced Concrete Structures in Seismic Prone Regions Case Study: Augusta Airship Hangar, Sicily

    International Nuclear Information System (INIS)

    Cronin, Kelly; Whyte, Catherine; Reiner, Tom

    2008-01-01

    Throughout the world there are hundreds of historic monuments and structures considered to be invaluable and irreplaceable. They are symbols of cultural identity and a means of educating people about history. Preservation of historic monuments and structures is therefore an important part of safeguarding these cultural heritage sites so that they retain their value for future generations.This report discusses a procedure for the investigation of seismic hazards in existing buildings and possible steps that can be taken to avoid damage caused by these hazards. The Augusta Airship Hangar located in Sicily, will be used as a case study however the topics addressed in this paper can be applied to other structures of historic value around the world.First state-of-the-art scanning procedures were used to create scale digital models that were imported into a structural analysis program. Within this program dynamic analyses were performed on the model based on actual ground motions taken close to the site. This data was used to determine the period and mode shapes of the structure. Then a nonlinear analysis, including a static pushover analysis, was implemented on a two-dimensional model of the structural frame. From this analysis the failure mechanisms of the structure were revealed with relation to an allowable roof displacement. The structural integrity of the structure was evaluated based on pre-defined performance goals. Finally multiple suggestions were made how the Augusta Airship Hangar might be repaired and strengthened so that this structure will not be destroyed should an earthquake occur.The results of our study show that historic structures, despite their age, can still be strong and ductile. Also there are a multitude of effective preservation and retrofit techniques that can be used to strengthen these historic structures, should an earthquake occur. Through this study, the Augusta Airship Hangar has proven to be not only a historic symbol for Sicily but

  13. Seismic fault analysis of Chicoutimi region

    International Nuclear Information System (INIS)

    Woussen, G.; Ngandee, S.

    1996-01-01

    On November 25, 1988, an earthquake measuring 6.5 on the Richter Scale occurred at a depth of 29 km in Precambrian bedrock in the Saguenay Region (Quebec). Given that the seismic event was located near a major zone of normal faults, it is important to determine if the earthquake could be associated with this large structure or with faults associated with this structure. This is discussed through a compilation and interpretation of structural discontinuities on key outcrops in the vicinity of the epicenter. The report is broken in four parts. The first part gives a brief overview of the geology in order to provide a geologic context for the structural measurements. The second comprises an analysis of fractures in each of the three lithotectonic units defined in the first part. The third part discusses the data and the fourth provides a conclusion. 30 refs., 53 figs

  14. Multicomponent ensemble models to forecast induced seismicity

    Science.gov (United States)

    Király-Proag, E.; Gischig, V.; Zechar, J. D.; Wiemer, S.

    2018-01-01

    In recent years, human-induced seismicity has become a more and more relevant topic due to its economic and social implications. Several models and approaches have been developed to explain underlying physical processes or forecast induced seismicity. They range from simple statistical models to coupled numerical models incorporating complex physics. We advocate the need for forecast testing as currently the best method for ascertaining if models are capable to reasonably accounting for key physical governing processes—or not. Moreover, operational forecast models are of great interest to help on-site decision-making in projects entailing induced earthquakes. We previously introduced a standardized framework following the guidelines of the Collaboratory for the Study of Earthquake Predictability, the Induced Seismicity Test Bench, to test, validate, and rank induced seismicity models. In this study, we describe how to construct multicomponent ensemble models based on Bayesian weightings that deliver more accurate forecasts than individual models in the case of Basel 2006 and Soultz-sous-Forêts 2004 enhanced geothermal stimulation projects. For this, we examine five calibrated variants of two significantly different model groups: (1) Shapiro and Smoothed Seismicity based on the seismogenic index, simple modified Omori-law-type seismicity decay, and temporally weighted smoothed seismicity; (2) Hydraulics and Seismicity based on numerically modelled pore pressure evolution that triggers seismicity using the Mohr-Coulomb failure criterion. We also demonstrate how the individual and ensemble models would perform as part of an operational Adaptive Traffic Light System. Investigating seismicity forecasts based on a range of potential injection scenarios, we use forecast periods of different durations to compute the occurrence probabilities of seismic events M ≥ 3. We show that in the case of the Basel 2006 geothermal stimulation the models forecast hazardous levels

  15. Reassessment of probabilistic seismic hazard in the Marmara region

    Science.gov (United States)

    Kalkan, Erol; Gulkan, Polat; Yilmaz, Nazan; Çelebi, Mehmet

    2009-01-01

    In 1999, the eastern coastline of the Marmara region (Turkey) witnessed increased seismic activity on the North Anatolian fault (NAF) system with two damaging earthquakes (M 7.4 Kocaeli and M 7.2 D??zce) that occurred almost three months apart. These events have reduced stress on the western segment of the NAF where it continues under the Marmara Sea. The undersea fault segments have been recently explored using bathymetric and reflection surveys. These recent findings helped scientists to understand the seismotectonic environment of the Marmara basin, which has remained a perplexing tectonic domain. On the basis of collected new data, seismic hazard of the Marmara region is reassessed using a probabilistic approach. Two different earthquake source models: (1) the smoothed-gridded seismicity model and (2) fault model and alternate magnitude-frequency relations, Gutenberg-Richter and characteristic, were used with local and imported ground-motion-prediction equations. Regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 sec on uniform firm-rock site condition (760 m=sec average shear wave velocity in the upper 30 m). These acceleration levels were computed for ground motions having 2% and 10% probabilities of exceedance in 50 yr, corresponding to return periods of about 2475 and 475 yr, respectively. The maximum PGA computed (at rock site) is 1.5g along the fault segments of the NAF zone extending into the Marmara Sea. The new maps generally show 10% to 15% increase for PGA, 0.2 and 1.0 sec spectral acceleration values across much of Marmara compared to previous regional hazard maps. Hazard curves and smooth design spectra for three site conditions: rock, soil, and soft-soil are provided for the Istanbul metropolitan area as possible tools in future risk estimates.

  16. The lithospheric structure of the Western Carpathian-Pannonian Basin region based on the CELEBRATION 2000 seismic experiment and gravity modelling

    Science.gov (United States)

    Tašárová, Alasonati; Afonso, J. C.; Bielik, M.; Götze, H.-J.; Hók, J.

    2009-10-01

    The lithospheric structure of the Western Carpathian-Pannonian Basin region was studied using 3-D modelling of the Bouguer gravity anomaly constrained by seismic models and other geophysical data. The thermal structure and density distribution in the shallow upper mantle were also estimated using a combination of petrological, geophysical, and mineral physics information (LitMod). This approach is necessary if the more complicated structure of the Pannonian Basin is to be better constrained. As a result, we have constructed the first 3-D gravity model of the region that combines various geophysical datasets and is consistent with petrological data. The model provides improved estimates of both the density distribution within the lithosphere and the depth to major density discontinuities. We present new maps of the thickness of major sedimentary basins and of the depth to the Moho and the lithosphere-asthenosphere boundary. In our best-fitting model, the Pannonian Basin is characterised by extremely thin crust and lithospheric mantle, both of which have low density. A low-density uppermost asthenospheric mantle layer is also included at depths of 60-100 km. The Western Carpathians have only a thin crustal root and moderate densities. In contrast, the European Platform and Eastern Alps are characterised by lithosphere that is considerably thicker and denser. This inference is also supported by stripped gravity anomalies from which sediment, Moho and asthenospheric gravity contributions have been removed. These residual anomalies are characteristically low in the Western Carpathian-Pannonian Basin region, which suggests that both the ALCAPA and Tisza-Dacia microplates are 'exotic terranes' that are markedly different to the European Platform.

  17. A procedure for seismic risk reduction in Campania Region

    Science.gov (United States)

    Zuccaro, G.; Palmieri, M.; Maggiò, F.; Cicalese, S.; Grassi, V.; Rauci, M.

    2008-07-01

    The Campania Region has set and performed a peculiar procedure in the field of seismic risk reduction. Great attention has been paid to public strategic buildings such as town halls, civil protection buildings and schools. The Ordinance 3274 promulgate in the 2004 by the Italian central authority obliged the owners of strategic buildings to perform seismic analyses within 2008 in order to check the safety of the structures and the adequacy to the use. In the procedure the Campania region, instead of the local authorities, ensure the complete drafting of seismic checks through financial resources of the Italian Government. A regional scientific technical committee has been constituted, composed of scientific experts, academics in seismic engineering. The committee has drawn up guidelines for the processing of seismic analyses. At the same time, the Region has issued a public competition to select technical seismic engineering experts to appoint seismic analysis in accordance with guidelines. The scientific committee has the option of requiring additional documents and studies in order to approve the safety checks elaborated. The Committee is supported by a technical and administrative secretariat composed of a group of expert in seismic engineering. At the moment several seismic safety checks have been completed. The results will be presented in this paper. Moreover, the policy to mitigate the seismic risk, set by Campania region, was to spend the most of the financial resources available on structural strengthening of public strategic buildings rather than in safety checks. A first set of buildings of which the response under seismic action was already known by data and studies of vulnerability previously realised, were selected for immediate retrofitting designs. Secondly, an other set of buildings were identified for structural strengthening. These were selected by using the criteria specified in the Guide Line prepared by the Scientific Committee and based on

  18. A procedure for seismic risk reduction in Campania Region

    International Nuclear Information System (INIS)

    Zuccaro, G.; Palmieri, M.; Cicalese, S.; Grassi, V.; Rauci, M.; Maggio, F.

    2008-01-01

    The Campania Region has set and performed a peculiar procedure in the field of seismic risk reduction. Great attention has been paid to public strategic buildings such as town halls, civil protection buildings and schools. The Ordinance 3274 promulgate in the 2004 by the Italian central authority obliged the owners of strategic buildings to perform seismic analyses within 2008 in order to check the safety of the structures and the adequacy to the use. In the procedure the Campania region, instead of the local authorities, ensure the complete drafting of seismic checks through financial resources of the Italian Government. A regional scientific technical committee has been constituted, composed of scientific experts, academics in seismic engineering. The committee has drawn up guidelines for the processing of seismic analyses. At the same time, the Region has issued a public competition to select technical seismic engineering experts to appoint seismic analysis in accordance with guidelines. The scientific committee has the option of requiring additional documents and studies in order to approve the safety checks elaborated. The Committee is supported by a technical and administrative secretariat composed of a group of expert in seismic engineering. At the moment several seismic safety checks have been completed. The results will be presented in this paper. Moreover, the policy to mitigate the seismic risk, set by Campania region, was to spend the most of the financial resources available on structural strengthening of public strategic buildings rather than in safety checks. A first set of buildings of which the response under seismic action was already known by data and studies of vulnerability previously realised, were selected for immediate retrofitting designs. Secondly, an other set of buildings were identified for structural strengthening. These were selected by using the criteria specified in the Guide Line prepared by the Scientific Committee and based on

  19. Moment-ration imaging of seismic regions for earthquake prediction

    Science.gov (United States)

    Lomnitz, Cinna

    1993-10-01

    An algorithm for predicting large earthquakes is proposed. The reciprocal ratio (mri) of the residual seismic moment to the total moment release in a region is used for imaging seismic moment precursors. Peaks in mri predict recent major earthquakes, including the 1985 Michoacan, 1985 central Chile, and 1992 Eureka, California earthquakes.

  20. Operations plan for the Regional Seismic Test Network

    International Nuclear Information System (INIS)

    1981-01-01

    The Regional Seismic Test Network program was established to provide a capability for detection of extremely sensitive earth movements. Seismic signals from both natural and man-made earth motions will be analyzed with the ultimate objective of accurately locating underground nuclear explosions. The Sandia National Laboratories, Albuquerque, has designed an unattended seismic station capable of recording seismic information received at the location of the seismometers installed as part of that specific station. A network of stations is required to increase the capability of determining the source of the seismic signal and the location of the source. Current plans are to establish a five-station seismic network in the United States and Canada. The Department of Energy, Nevada Operations Office, has been assigned the responsibility for deploying, installing, and operating these remote stations. This Operation Plan provides the basic information and tasking to accomplish this assignment

  1. Indication to distinguish the burst region of coal gas from seismic data

    Energy Technology Data Exchange (ETDEWEB)

    Jian-yuan Cheng; Hong-wei Tang; Lin Xu; Yan-fang Li [China Coal Research Institute, Xi' an (China). Xi' an Research Institute

    2009-09-15

    The velocity of an over-burst coal seam is about 1/3 compared to a normal coal seam based on laboratory test results. This can be considered as a basis to confirm the area of coal and gas burst by seismic exploration technique. Similarly, the simulation result of the theoretical seismic model shows that there is obvious distinction between over-burst coal and normal coal based on the coal reflection's travel-time, energy and frequency. The results from the actual seismic data acquired in the coal and gas over-burst cases is consistent with that of the laboratory and seismic modeling; that is, in the coal and gas burst region, seismic reflection travel time is delayed, seismic amplitude is weakened and seismic frequency is reduced. Therefore, it can be concluded that seismic exploration technique is promising for use in distinguishing coal and gas over-burst regions based on the variation of seismic reflection travel time, amplitude and frequency. 7 refs., 6 figs.

  2. Seismic waveform modeling over cloud

    Science.gov (United States)

    Luo, Cong; Friederich, Wolfgang

    2016-04-01

    With the fast growing computational technologies, numerical simulation of seismic wave propagation achieved huge successes. Obtaining the synthetic waveforms through numerical simulation receives an increasing amount of attention from seismologists. However, computational seismology is a data-intensive research field, and the numerical packages usually come with a steep learning curve. Users are expected to master considerable amount of computer knowledge and data processing skills. Training users to use the numerical packages, correctly access and utilize the computational resources is a troubled task. In addition to that, accessing to HPC is also a common difficulty for many users. To solve these problems, a cloud based solution dedicated on shallow seismic waveform modeling has been developed with the state-of-the-art web technologies. It is a web platform integrating both software and hardware with multilayer architecture: a well designed SQL database serves as the data layer, HPC and dedicated pipeline for it is the business layer. Through this platform, users will no longer need to compile and manipulate various packages on the local machine within local network to perform a simulation. By providing users professional access to the computational code through its interfaces and delivering our computational resources to the users over cloud, users can customize the simulation at expert-level, submit and run the job through it.

  3. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    Science.gov (United States)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  4. Seismic Tomography of Siyazan - Shabran Oil and Gas Region Of Azerbaijan by Data of The Seismic Stations

    Science.gov (United States)

    Yetirmishli, Gurban; Guliyev, Ibrahim; Mammadov, Nazim; Kazimova, Sabina; Ismailova, Saida

    2016-04-01

    The main purpose of the research was to build a reliable 3D model of the structure of seismic velocities in the earth crust on the territory of Siyazan-Shabran region of Azerbaijan, using the data of seismic telemetry stations spanning Siyazan-Shabran region (Siyazan, Altiagaj, Pirgulu, Guba, Khinalig, Gusar), including 7 mobile telemetry seismic stations. Interest to the problem of research seismic tomography caused by applied environmental objectives, such as the assessment of geological risks, engineering evaluation (stability and safety of wells), the task of exploration and mining operations. In the study region are being actively developed oil fields, and therefore, there is a risk of technogenic earthquakes. It was performed the calculation of first arrival travel times of P and S waves and the corresponding ray paths. Calculate 1D velocity model which is the initial model as a set of horizontal layers (velocity may be constant or changed linearly with depth on each layer, gaps are possible only at the boundaries between the layers). Have been constructed and analyzed the horizontal sections of the three-dimensional velocity model at different depths of the investigated region. By the empirical method was proposed density model of the sedimentary rocks at depths of 0-8 km.

  5. Observations and modeling of seismic background noise

    Science.gov (United States)

    Peterson, Jon R.

    1993-01-01

    The preparation of this report had two purposes. One was to present a catalog of seismic background noise spectra obtained from a worldwide network of seismograph stations. The other purpose was to refine and document models of seismic background noise that have been in use for several years. The second objective was, in fact, the principal reason that this study was initiated and influenced the procedures used in collecting and processing the data.With a single exception, all of the data used in this study were extracted from the digital data archive at the U.S. Geological Survey's Albuquerque Seismological Laboratory (ASL). This archive dates from 1972 when ASL first began deploying digital seismograph systems and collecting and distributing digital data under the sponsorship of the Defense Advanced Research Projects Agency (DARPA). There have been many changes and additions to the global seismograph networks during the past twenty years, but perhaps none as significant as the current deployment of very broadband seismographs by the U.S. Geological Survey (USGS) and the University of California San Diego (UCSD) under the scientific direction of the IRIS consortium. The new data acquisition systems have extended the bandwidth and resolution of seismic recording, and they utilize high-density recording media that permit the continuous recording of broadband data. The data improvements and continuous recording greatly benefit and simplify surveys of seismic background noise.Although there are many other sources of digital data, the ASL archive data were used almost exclusively because of accessibility and because the data systems and their calibration are well documented for the most part. Fortunately, the ASL archive contains high-quality data from other stations in addition to those deployed by the USGS. Included are data from UCSD IRIS/IDA stations, the Regional Seismic Test Network (RSTN) deployed by Sandia National Laboratories (SNL), and the TERRAscope network

  6. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    Energy Technology Data Exchange (ETDEWEB)

    Lestari, Titik, E-mail: t2klestari@gmail.com [Meteorological Climatological and Geophysical Agency (MCGA), Jalan Angkasa I No.2 Kemayoran, Jakarta Pusat, 10720 (Indonesia); Faculty of Earth Science and Technology, Bandung Institute of Technology, Jalan Ganesa No.10, Bandung 40132 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Global Geophysical Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology, Jalan Ganesa 10 Bandung 40132 (Indonesia)

    2015-04-24

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  7. Seismic hazard assessment in the Ibero-Maghreb region

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, M.J.; Garcia fernandez, M. [Consejo Superior de Investigaciones Cientifcas, Barcelona (Spain). Inst. of Earth Sciences; GSAHP Ibero-Maghreb Working Group

    1999-12-01

    The paper illustrates the contribution of the Ibero-Maghreb region to the global GSHAP (Global Seismic Hazard Assessment Program) map: for the first time, a map of regional hazard source zones is presented and agreement on a common procedure for hazard computation in the region has been achieved.

  8. Probabilistic Seismic Hazard Assessment for Northeast India Region

    Science.gov (United States)

    Das, Ranjit; Sharma, M. L.; Wason, H. R.

    2016-08-01

    Northeast India bounded by latitudes 20°-30°N and longitudes 87°-98°E is one of the most seismically active areas in the world. This region has experienced several moderate-to-large-sized earthquakes, including the 12 June, 1897 Shillong earthquake ( M w 8.1) and the 15 August, 1950 Assam earthquake ( M w 8.7) which caused loss of human lives and significant damages to buildings highlighting the importance of seismic hazard assessment for the region. Probabilistic seismic hazard assessment of the region has been carried out using a unified moment magnitude catalog prepared by an improved General Orthogonal Regression methodology (Geophys J Int, 190:1091-1096, 2012; Probabilistic seismic hazard assessment of Northeast India region, Ph.D. Thesis, Department of Earthquake Engineering, IIT Roorkee, Roorkee, 2013) with events compiled from various databases (ISC, NEIC,GCMT, IMD) and other available catalogs. The study area has been subdivided into nine seismogenic source zones to account for local variation in tectonics and seismicity characteristics. The seismicity parameters are estimated for each of these source zones, which are input variables into seismic hazard estimation of a region. The seismic hazard analysis of the study region has been performed by dividing the area into grids of size 0.1° × 0.1°. Peak ground acceleration (PGA) and spectral acceleration ( S a) values (for periods of 0.2 and 1 s) have been evaluated at bedrock level corresponding to probability of exceedance (PE) of 50, 20, 10, 2 and 0.5 % in 50 years. These exceedance values correspond to return periods of 100, 225, 475, 2475, and 10,000 years, respectively. The seismic hazard maps have been prepared at the bedrock level, and it is observed that the seismic hazard estimates show a significant local variation in contrast to the uniform hazard value suggested by the Indian standard seismic code [Indian standard, criteria for earthquake-resistant design of structures, fifth edition, Part

  9. The New Italian Seismic Hazard Model

    Science.gov (United States)

    Marzocchi, W.; Meletti, C.; Albarello, D.; D'Amico, V.; Luzi, L.; Martinelli, F.; Pace, B.; Pignone, M.; Rovida, A.; Visini, F.

    2017-12-01

    In 2015 the Seismic Hazard Center (Centro Pericolosità Sismica - CPS) of the National Institute of Geophysics and Volcanology was commissioned of coordinating the national scientific community with the aim to elaborate a new reference seismic hazard model, mainly finalized to the update of seismic code. The CPS designed a roadmap for releasing within three years a significantly renewed PSHA model, with regard both to the updated input elements and to the strategies to be followed. The main requirements of the model were discussed in meetings with the experts on earthquake engineering that then will participate to the revision of the building code. The activities were organized in 6 tasks: program coordination, input data, seismicity models, ground motion predictive equations (GMPEs), computation and rendering, testing. The input data task has been selecting the most updated information about seismicity (historical and instrumental), seismogenic faults, and deformation (both from seismicity and geodetic data). The seismicity models have been elaborating in terms of classic source areas, fault sources and gridded seismicity based on different approaches. The GMPEs task has selected the most recent models accounting for their tectonic suitability and forecasting performance. The testing phase has been planned to design statistical procedures to test with the available data the whole seismic hazard models, and single components such as the seismicity models and the GMPEs. In this talk we show some preliminary results, summarize the overall strategy for building the new Italian PSHA model, and discuss in detail important novelties that we put forward. Specifically, we adopt a new formal probabilistic framework to interpret the outcomes of the model and to test it meaningfully; this requires a proper definition and characterization of both aleatory variability and epistemic uncertainty that we accomplish through an ensemble modeling strategy. We use a weighting scheme

  10. Salton Trough Post-seismic Afterslip, Viscoelastic Response, and Contribution to Regional Hazard

    Science.gov (United States)

    Parker, J. W.; Donnellan, A.; Lyzenga, G. A.

    2012-12-01

    The El Mayor-Cucapah M7.2 April 4 2010 earthquake in Baja California may have affected accumulated hazard to Southern California cities due to loading of regional faults including the Elsinore, San Jacinto and southern San Andreas, faults which already have over a century of tectonic loading. We examine changes observed via multiple seismic and geodetic techniques, including micro seismicity and proposed seismicity-based indicators of hazard, high-quality fault models, the Plate Boundary Observatory GNSS array (with 174 stations showing post-seismic transients with greater than 1 mm amplitude), and interferometric radar maps from UAVSAR (aircraft) flights, showing a network of aseismic fault slip events at distances up to 60 km from the end of the surface rupture. Finite element modeling is used to compute the expected coseismic motions at GPS stations with general agreement, including coseismic uplift at sites ~200 km north of the rupture. Postseismic response is also compared, with GNSS and also with the CIG software "RELAX." An initial examination of hazard is made comparing micro seismicity-based metrics, fault models, and changes to coulomb stress on nearby faults using the finite element model. Comparison of seismicity with interferograms and historic earthquakes show aseismic slip occurs on fault segments that have had earthquakes in the last 70 years, while other segments show no slip at the surface but do show high triggered seismicity. UAVSAR-based estimates of fault slip can be incorporated into the finite element model to correct Coloumb stress change.

  11. Seismic and Tectonic Regionalization of the State of Michoacan.

    Science.gov (United States)

    Vazquez Rosas, R.; Aguirre, J.; Garduño-Monroy, V. H.; Ramirez-Guzman, L.

    2017-12-01

    In Mexico it is a country with seismically active regions, mainly the zones that are next to the pacific where the zone of subduction is located, in this work we focus on the state of Michoacán, since this has not been completely studied in the last 30 years after the earthquake in Michoacán in 1985. The first most important step is to know the region which are the most seismic zones within the state and one way is to carry out the regionalization of Michoacán identifying the sources of earthquakes as well as where occur more frequently.If we could know each of the factors that influence seismicity and describe every point of the terrain, every rupture, every rock, etc., then we could describe in an analytical way the seismic process and predict the occurrence of earthquakes such as eclipses. Unfortunately the number of parameters is so enormous that we cannot arrive at an exact description; however, we can take advantage of statistical properties to evaluate probabilities, even in the case of small systems such as a particular seismic zone.In this paper, epicenter data were collected from 1970 to 2014, and with them a statistical study was carried out and the epicenter data plotted using data reported by the National Seismological Service and the IRIS catalog as well as some data from the Institute of engineering UNAM. Where earthquakes of equal and greater than M = 4 were used. Graphing these in function with the depth and with that it was graficaron and was made an overlapping the faults of the state and with that it was divided in 4 seismic zones in function of the faults and the localized seismicity.Zone A. is located within the Michoacán Block set of faults, as well as part of the subduction zone on the coast of the state. Seismicity in this area is high. Zone B-1. This is located between the limits of Jalisco and Michoacán in the set of faults called Tepalcatepec depression and limits with the Jorullo-Tacámbaro fracture. At this site seismicity is

  12. An alternative approach to probabilistic seismic hazard analysis in the Aegean region using Monte Carlo simulation

    Science.gov (United States)

    Weatherill, Graeme; Burton, Paul W.

    2010-09-01

    The Aegean is the most seismically active and tectonically complex region in Europe. Damaging earthquakes have occurred here throughout recorded history, often resulting in considerable loss of life. The Monte Carlo method of probabilistic seismic hazard analysis (PSHA) is used to determine the level of ground motion likely to be exceeded in a given time period. Multiple random simulations of seismicity are generated to calculate, directly, the ground motion for a given site. Within the seismic hazard analysis we explore the impact of different seismic source models, incorporating both uniform zones and distributed seismicity. A new, simplified, seismic source model, derived from seismotectonic interpretation, is presented for the Aegean region. This is combined into the epistemic uncertainty analysis alongside existing source models for the region, and models derived by a K-means cluster analysis approach. Seismic source models derived using the K-means approach offer a degree of objectivity and reproducibility into the otherwise subjective approach of delineating seismic sources using expert judgment. Similar review and analysis is undertaken for the selection of peak ground acceleration (PGA) attenuation models, incorporating into the epistemic analysis Greek-specific models, European models and a Next Generation Attenuation model. Hazard maps for PGA on a "rock" site with a 10% probability of being exceeded in 50 years are produced and different source and attenuation models are compared. These indicate that Greek-specific attenuation models, with their smaller aleatory variability terms, produce lower PGA hazard, whilst recent European models and Next Generation Attenuation (NGA) model produce similar results. The Monte Carlo method is extended further to assimilate epistemic uncertainty into the hazard calculation, thus integrating across several appropriate source and PGA attenuation models. Site condition and fault-type are also integrated into the hazard

  13. A New Seismic Hazard Model for Mainland China

    Science.gov (United States)

    Rong, Y.; Xu, X.; Chen, G.; Cheng, J.; Magistrale, H.; Shen, Z. K.

    2017-12-01

    We are developing a new seismic hazard model for Mainland China by integrating historical earthquake catalogs, geological faults, geodetic GPS data, and geology maps. To build the model, we construct an Mw-based homogeneous historical earthquake catalog spanning from 780 B.C. to present, create fault models from active fault data, and derive a strain rate model based on the most complete GPS measurements and a new strain derivation algorithm. We divide China and the surrounding regions into about 20 large seismic source zones. For each zone, a tapered Gutenberg-Richter (TGR) magnitude-frequency distribution is used to model the seismic activity rates. The a- and b-values of the TGR distribution are calculated using observed earthquake data, while the corner magnitude is constrained independently using the seismic moment rate inferred from the geodetically-based strain rate model. Small and medium sized earthquakes are distributed within the source zones following the location and magnitude patterns of historical earthquakes. Some of the larger earthquakes are distributed onto active faults, based on their geological characteristics such as slip rate, fault length, down-dip width, and various paleoseismic data. The remaining larger earthquakes are then placed into the background. A new set of magnitude-rupture scaling relationships is developed based on earthquake data from China and vicinity. We evaluate and select appropriate ground motion prediction equations by comparing them with observed ground motion data and performing residual analysis. To implement the modeling workflow, we develop a tool that builds upon the functionalities of GEM's Hazard Modeler's Toolkit. The GEM OpenQuake software is used to calculate seismic hazard at various ground motion periods and various return periods. To account for site amplification, we construct a site condition map based on geology. The resulting new seismic hazard maps can be used for seismic risk analysis and management.

  14. Seismic acceleration map expected for Japanese central region

    International Nuclear Information System (INIS)

    Sugiyama, Takeshi; Maeda, Kouji; Ishii, Kiyoshi; Suzuki, Makoto.

    1990-01-01

    Since electric generating and supplying facilities scatter in large areas, the seismic acceleration map, which defines the anticipated earthquake ground motions in a broad region, is very useful information for the design of those facilities against large earthquakes. This paper describes the development of a seismic acceleration map for the Central Japanese Region by incorporating the analytical results based on historical earthquake records and active fault data using probability and statistics. In the region, there have occurred several destructive earthquakes; Anseitokai (1854, M = 8.4) and Tohnankai (1944, M = 7.9) earthquakes along the Nankai trough; Nohbi (1891, M = 8.0) and Fukui (1948, M = 7.1) earthquakes in inland ares. Some of the historical earthquake data were obtained by instrument last one hundred years, whereas others by literary descriptions for nearly 1,000 years. The active fault data, have been collected mainly from the surveys of fault topography and geology, and are considered to indicate the average seismic activity for the past million years. A proposed seismic acceleration map for the return period of 75 years, calculated on the free surface of base stratum, was estimated by the following way. The analytical result based on the historical earthquake records was adopted mainly, because the Japanese seismic design criteria have been developed based on them. The proposed seismic acceleration map was revised by including the result based on the active fault data for the areas, where historical earthquake records lack, and the result was smoothed to evaluate the final seismic acceleration map. (author)

  15. Seismic spectra of events at regional distances

    International Nuclear Information System (INIS)

    Springer, D.L.; Denny, M.D.

    1976-01-01

    About 40 underground nuclear explosions detonated at the Nevada Test Site (NTS) were chosen for analysis of their spectra and any relationships they might have to source parameters such as yield, depth of burial, etc. The sample covered a large yield range (less than 20 kt to greater than 1 Mt). Broadband (0.05 to 20 Hz) data recorded by the four-station seismic network operated by Lawrence Livermore Laboratory were analyzed in a search for unusual explosion signatures in their spectra. Long time windows (total wave train) as well as shorter windows (for instance, P/sub n/) were used as input to calculate the spectra. Much variation in the spectra of the long windows is typical although some gross features are similar, such as a dominant peak in the microseismic window. The variation is such that selection of corner frequencies is impractical and yield scaling could not be determined. Spectra for one NTS earthquake showed more energy in the short periods (less than 1 sec) as well as in the long periods (greater than 8 sec) compared to those for NTS explosions

  16. Seismic data restoration with a fast L1 norm trust region method

    International Nuclear Information System (INIS)

    Cao, Jingjie; Wang, Yanfei

    2014-01-01

    Seismic data restoration is a major strategy to provide reliable wavefield when field data dissatisfy the Shannon sampling theorem. Recovery by sparsity-promoting inversion often get sparse solutions of seismic data in a transformed domains, however, most methods for sparsity-promoting inversion are line-searching methods which are efficient but are inclined to obtain local solutions. Using trust region method which can provide globally convergent solutions is a good choice to overcome this shortcoming. A trust region method for sparse inversion has been proposed, however, the efficiency should be improved to suitable for large-scale computation. In this paper, a new L 1 norm trust region model is proposed for seismic data restoration and a robust gradient projection method for solving the sub-problem is utilized. Numerical results of synthetic and field data demonstrate that the proposed trust region method can get excellent computation speed and is a viable alternative for large-scale computation. (paper)

  17. Applicability of deterministic methods in seismic site effects modeling

    International Nuclear Information System (INIS)

    Cioflan, C.O.; Radulian, M.; Apostol, B.F.; Ciucu, C.

    2005-01-01

    The up-to-date information related to local geological structure in the Bucharest urban area has been integrated in complex analyses of the seismic ground motion simulation using deterministic procedures. The data recorded for the Vrancea intermediate-depth large earthquakes are supplemented with synthetic computations all over the city area. The hybrid method with a double-couple seismic source approximation and a relatively simple regional and local structure models allows a satisfactory reproduction of the strong motion records in the frequency domain (0.05-1)Hz. The new geological information and a deterministic analytical method which combine the modal summation technique, applied to model the seismic wave propagation between the seismic source and the studied sites, with the mode coupling approach used to model the seismic wave propagation through the local sedimentary structure of the target site, allows to extend the modelling to higher frequencies of earthquake engineering interest. The results of these studies (synthetic time histories of the ground motion parameters, absolute and relative response spectra etc) for the last 3 Vrancea strong events (August 31,1986 M w =7.1; May 30,1990 M w = 6.9 and October 27, 2004 M w = 6.0) can complete the strong motion database used for the microzonation purposes. Implications and integration of the deterministic results into the urban planning and disaster management strategies are also discussed. (authors)

  18. Seismicity, seismic input and site effects in the Sahel-Algiers region (north Algeria)

    International Nuclear Information System (INIS)

    Harbi, A.; Maouche, S.; Oussadou, F.; Vaccari, F.; Aoudia, A.; Panza, G.F.; Benouar, D.

    2005-07-01

    Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this capital city, a realistic modelling of the seismic ground motion using the hybrid method that combines the finite-differences method and the modal summation, is conducted. For this purpose, a complete database in terms of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone (2.25 deg. E-3.50 deg. E, 36.50 deg. N-37.00 deg. N) is performed and an earthquake list, for the period 1359-2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross-sections have been built up to model the seismic ground motion in the city, caused by the 1989 Mont-Chenoua and the 1924 Douera earthquakes; a set of synthetic seismograms and response spectral ratio is produced for Algiers. The numerical results show that the soft sediments in Algiers centre are responsible of the noticed amplification of the seismic ground motion. (author)

  19. Seismic stratigraphy and regional unconformity analysis of Chukchi Sea Basins

    Science.gov (United States)

    Agasheva, Mariia; Karpov, Yury; Stoupakova, Antonina; Suslova, Anna

    2017-04-01

    Russian Chukchi Sea Shelf one of petroleum potential province and still one of the most uninvestigated area. North and Sough Chukchi Trough that separated by Wrangel-Hearld Arch have different origin. The main challenge is stratigraphic sequences determination that filled North and South Chukchi basins. The joint tectonic evolution of the territory as Canada basin opening and Brooks Range-Wrangel Herald orogenic events enable to expect the analogous stratigraphy sequences in Russian Part. Analysis of 2D seismic data of Russian and American Chukchi Sea represent the major seismic reflectance that traced throughout the basins. Referring to this data North Chukchi basin includes four seismic stratigraphic sequences - Franklian (pre-Mississippian), Ellesmirian (Upper Devonian-Jurassic), Beaufortian (Jurassic-Lower Cretaceous) and Brookian (Lower Cretaceous-Cenozoic), as it is in North Slope Alaska [1]. South Chukchi basin has different tectonic nature, representing only Franclian basement and Brookian sequences. Sedimentary cover of North Chukchi basins starts with Ellesmirian sequence it is marked by bright reflector that separates from chaotic folded Franklian sequence. Lower Ellesmirian sequence fills of grabens that formed during upper Devonian rifting. Devonian extension event was initiated as a result of Post-Caledonian orogenic collapse, terminating with the opening of Arctic oceans. Beaufortian sequence is distinguished in Colville basin and Hanna Trough by seismically defined clinoforms. Paleozoic and Mesozoic strata are eroded by regional Lower Cretaceous Unconformity (LCU) linked with Canada basin opening. LCU is defined at seismic by angular unconformity, tracing at most arctic basins. Lower Cretaceous erosion and uplift event are of Hauterivian to Aptian age in Brooks Range and the Loppa High uplift refer to the early Barremian. The Lower Cretaceous clinoform complex downlaps to LCU horizon and filling North Chukchi basin (as in Colville basin Alska

  20. Analysis of the seismic catalogues for the Vrancea Region, Romania

    International Nuclear Information System (INIS)

    Romashkova, L.L.; Kossobokov, V.G.

    2005-11-01

    Vrancea (Romania) is a geographical region between Eastern and Southern Carpathian Mountains. The region is characterized by a rather high level of seismic activity mainly at intermediate (up to 200 km) depths. These intermediate-depth earthquakes occur between 45 deg-46 deg N and 26 deg-27 deg E. The shallow earthquakes are dispersed over a much broader territory. We performed the comparative analysis of earthquake catalogues available for Vrancea region aiming at the compilation of a data set, to be as complete and homogeneous as possible, which, hopefully, will be used for the prediction of strong and possibly moderate earthquakes in the region by means of M8 algorithm. The two catalogues under study are: 1) Global Hypocenter Data Base catalogue, NEIC (GHDB, 1989) and 2) local Vrancea seismic catalogue (Moldoveanu et al., 1995) and their updates. (author)

  1. Seismic quiescence in a frictional earthquake model

    Science.gov (United States)

    Braun, Oleg M.; Peyrard, Michel

    2018-04-01

    We investigate the origin of seismic quiescence with a generalized version of the Burridge-Knopoff model for earthquakes and show that it can be generated by a multipeaked probability distribution of the thresholds at which contacts break. Such a distribution is not assumed a priori but naturally results from the aging of the contacts. We show that the model can exhibit quiescence as well as enhanced foreshock activity, depending on the value of some parameters. This provides a generic understanding for seismic quiescence, which encompasses earlier specific explanations and could provide a pathway for a classification of faults.

  2. Correlation Between Electromagnetic Signals and Seismic Events on Central Colombia Region to Establish Seismic Precursors Existence

    Science.gov (United States)

    Caneva, A.; Vargas Jiménez, C. A.; Solano Fino, J. M.

    2017-12-01

    It was already shown by several authors around the world some kinds of correlation between electric and magnetic signals and seismic events looking for precursors to the last ones emitted from the seismic source. This investigation tends to establish a correlation between electro-magnetic (EM) signals on the ground surface and seismic events on the Colombian lithospheric system. The events correlation was made with data from the Seismological Network of the Sabana de Bogotá (RSSB for its acronym in Spanish), a temporal seismological network on Chichimene (Acacías, Meta, Colombia) and the National Seismological Network of Colombia (RSNC, for its acronym in Spanish). The project involved the design, construction and preliminary tests for the necessary instruments added to the RSSB as multi-parameter stations with seismic broadband, electric polarizing and non-polarizing dipoles and Earth's magnetic field sensors. Correlations were made considering time, frequency and `natural time' domains with filtering and preprocessing algorithms. Among the main results are the almost complete lack of electric disturbances known as Seismic Electric Signals (SES) and very few of the magnetic kind. However, another kind of long period magnetic disturbances for some stations and events where found. More instruments have to be deployed in order to get a better understanding of these disturbances and develop a robust model.

  3. Detailed seismicity analysis in the SE of Romania (Dobrogea region)

    Science.gov (United States)

    Rogozea, Maria; Radulian, Mircea; Ghica, Daniela; Popa, Mihaela

    2014-05-01

    The purpose of this paper is to analyze the seismicity in the south-eastern part of Romania, in the Dobrogea region (namely the Predobrogean Depression and Black Sea area). Predobrogean Depression is the name attributed to the structures belonging to the Scythian Platform. The seismic activity is moderate with most significant earthquakes at the boundary between the North Dobrogea Orogen and Scythian Platform (Sf. Gheorghe fault). The largest magnitude event was recorded in 02.11.1871 (Mw = 5.3). Other events with magnitude above 4 were observed close to Tulcea city (13.11.1981, Mw = 5.1, 03.09.204, Mw =5.1) and Galati city (11.09.1980, Mw = 4.2). Recently, an earthquake swarm of 406 events extended over two months and a half (23 September - 5 December 2013) was produced in the Galati area (maximum magnitude 3.9). The deformation field has an extensional regime, as resulted from fault plane solutions and geotectonic investigations. The maximum expected magnitude in this area is estimated at Mw = 5.5. The seismic activity in the Black Sea area, close to Romania seashore and north-east Bulgarian seashore, concentrates along Shabla fault system. Large shocks (magnitude above 7) are reported here at intervals of a few centuries. The most recent major shock was recorded on 31 January 1901 (Mw = 7.2) in Shabla region, Bulgaria. To characterize seismicity parameters, the Romanian catalogue of the National Institute of Earth Physics was used as a basic input. The catalogue was revised as concerns historical information by reanalyzing macroseismic data and for the recent events, by applying up-to-date tools to relocate and re-parametrize the seismic sources.

  4. Comparison between seismic and domestic risk in moderate seismic hazard prone region: the Grenoble City (France test site

    Directory of Open Access Journals (Sweden)

    F. Dunand

    2012-02-01

    Full Text Available France has a moderate level of seismic activity, characterized by diffuse seismicity, sometimes experiencing earthquakes of a magnitude of more than 5 in the most active zones. In this seismicity context, Grenoble is a city of major economic and social importance. However, earthquakes being rare, public authorities and the decision makers are only vaguely committed to reducing seismic risk: return periods are long and local policy makers do not have much information available. Over the past 25 yr, a large number of studies have been conducted to improve our knowledge of seismic hazard in this region. One of the decision-making concerns of Grenoble's public authorities, as managers of a large number of public buildings, is to know not only the seismic-prone regions, the variability of seismic hazard due to site effects and the city's overall vulnerability, but also the level of seismic risk and exposure for the entire city, also compared to other natural or/and domestic hazards. Our seismic risk analysis uses a probabilistic approach for regional and local hazards and the vulnerability assessment of buildings. Its applicability to Grenoble offers the advantage of being based on knowledge acquired by previous projects conducted over the years. This paper aims to compare the level of seismic risk with that of other risks and to introduce the notion of risk acceptability in order to offer guidance in the management of seismic risk. This notion of acceptability, which is now part of seismic risk consideration for existing buildings in Switzerland, is relevant in moderately seismic-prone countries like France.

  5. Ground temperature enhancements in seismic regions

    Science.gov (United States)

    Parrot, M.; Pokhotelov, O.; Surkov, V.; Hayakawa, M.

    In the past decade, numerous observations of surface and near surface temperature anomalies before earthquakes have been published. Monitoring of the seismo -active regions from space have been made in visible and infrared ranges by various satellites: NOOA satellites, UARS, TERRA and etc. This paper presents some examples of these observations. A review of different mechanisms to explain the phenomenon is given and a more detailed explanation of the mechanism proposed by the authors is presented. It is shown that long term temperature anomalies can arise due to the rock warming resulting from the underground water upward filtrating. However, the short term temperature anomalies observed several days before an earthquake, are due to the change in the specific heat capacity and in the heat conductivity of the soil induced by the variations of the moisture. This research is partially supported by the Commission of the EU (Grant No. INTAS-2001-0456), by ISTC through Research Grant No. 1121 and by Russian Fund for Basic Research through Grant No. 02-05-64612.

  6. Seismic security assessment of earth and rockfill dams located in epicentral regions

    Energy Technology Data Exchange (ETDEWEB)

    Oldecop, L.; Zabala, F.; Rodari, R. [San Juan National Univ., San Juan (Argentina). Instituto de Invest. Antisismicas

    2004-07-01

    The seismic safety of dams is of great interest to the midwest region of Argentina, the most seismically active area in the country. This paper examines factors controlling the design of dams subjected to earthquake action, criteria for safety verification and the analysis tools currently available. Data of dams, active faults and epicenters of historic earthquakes in the region were provided. Paleoseismicity research was suggested as an important area of research, potentially enhancing an understanding of a region's seismic activity. It was concluded that analysis tools currently used in engineering include simple models offering advantages in reliability and ease of result interpretation, but have shortcomings in their applicability. Care must be taken in the validation and interpretation of these models, particularly when the behaviour of a dam includes complex phenomena. More sophisticated analysis tools currently available are difficult to apply, largely due to the complexity of algorithms in the models. It was also concluded that in order to overcome difficulties in both simple and complex models, predictions should be contrasted with real behaviour data. Data from measurement of seismic behaviour is still relatively scarce, presenting an obstacle towards the further use of more sophisticated analysis tools, as they are not as yet tested against measurements and observations of real cases. 15 refs., 2 tabs., 11 figs.

  7. The SCEC Unified Community Velocity Model (UCVM) Software Framework for Distributing and Querying Seismic Velocity Models

    Science.gov (United States)

    Maechling, P. J.; Taborda, R.; Callaghan, S.; Shaw, J. H.; Plesch, A.; Olsen, K. B.; Jordan, T. H.; Goulet, C. A.

    2017-12-01

    Crustal seismic velocity models and datasets play a key role in regional three-dimensional numerical earthquake ground-motion simulation, full waveform tomography, modern physics-based probabilistic earthquake hazard analysis, as well as in other related fields including geophysics, seismology, and earthquake engineering. The standard material properties provided by a seismic velocity model are P- and S-wave velocities and density for any arbitrary point within the geographic volume for which the model is defined. Many seismic velocity models and datasets are constructed by synthesizing information from multiple sources and the resulting models are delivered to users in multiple file formats, such as text files, binary files, HDF-5 files, structured and unstructured grids, and through computer applications that allow for interactive querying of material properties. The Southern California Earthquake Center (SCEC) has developed the Unified Community Velocity Model (UCVM) software framework to facilitate the registration and distribution of existing and future seismic velocity models to the SCEC community. The UCVM software framework is designed to provide a standard query interface to multiple, alternative velocity models, even if the underlying velocity models are defined in different formats or use different geographic projections. The UCVM framework provides a comprehensive set of open-source tools for querying seismic velocity model properties, combining regional 3D models and 1D background models, visualizing 3D models, and generating computational models in the form of regular grids or unstructured meshes that can be used as inputs for ground-motion simulations. The UCVM framework helps researchers compare seismic velocity models and build equivalent simulation meshes from alternative velocity models. These capabilities enable researchers to evaluate the impact of alternative velocity models in ground-motion simulations and seismic hazard analysis applications

  8. Probabilistic Seismic Hazard Assessment for Himalayan-Tibetan Region from Historical and Instrumental Earthquake Catalogs

    Science.gov (United States)

    Rahman, M. Moklesur; Bai, Ling; Khan, Nangyal Ghani; Li, Guohui

    2018-02-01

    The Himalayan-Tibetan region has a long history of devastating earthquakes with wide-spread casualties and socio-economic damages. Here, we conduct the probabilistic seismic hazard analysis by incorporating the incomplete historical earthquake records along with the instrumental earthquake catalogs for the Himalayan-Tibetan region. Historical earthquake records back to more than 1000 years ago and an updated, homogenized and declustered instrumental earthquake catalog since 1906 are utilized. The essential seismicity parameters, namely, the mean seismicity rate γ, the Gutenberg-Richter b value, and the maximum expected magnitude M max are estimated using the maximum likelihood algorithm assuming the incompleteness of the catalog. To compute the hazard value, three seismogenic source models (smoothed gridded, linear, and areal sources) and two sets of ground motion prediction equations are combined by means of a logic tree on accounting the epistemic uncertainties. The peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2 and 1.0 s are predicted for 2 and 10% probabilities of exceedance over 50 years assuming bedrock condition. The resulting PGA and SA maps show a significant spatio-temporal variation in the hazard values. In general, hazard value is found to be much higher than the previous studies for regions, where great earthquakes have actually occurred. The use of the historical and instrumental earthquake catalogs in combination of multiple seismogenic source models provides better seismic hazard constraints for the Himalayan-Tibetan region.

  9. Implications of Seismically Active Fault Structures in Ankay and Alaotra Regions of Northern and Central Madagascar

    Science.gov (United States)

    Malloy, S.; Stamps, D. S.

    2017-12-01

    The purpose of the study is to gain a better understanding of the seismically active fault structures in central and northern Madagascar. We study the Ankay and Lake Alaotra regions of Madagascar, which are segmented by multiple faults that strike N-S. In general, normal seismic events occur on faults bounding the Alaotra-Ankay rift basin where Quaternary alluvium is present. Due to this pattern and moderate amounts of low magnitude seismic activity along these faults, it is hypothesized the region currently undergoes E-W extension. In this work we test how variations in fault strength and net slip changes influence expected crustal movement in the region. Using the Coulomb stress failure point as a test of strength we are able to model the Alaotra-Ankay region using MATLAB Coulomb 3.3.01. This program allows us to define realistic Poisson's ratio and Young's modulus of mapped rock compositions in the region, i.e. paragneiss and orthogneiss, create 3D fault geometries, and calculate static stress changes with coinciding surface displacements. We impose slip along multiple faults and calculate seismic moment that we balance by the 3 observed earthquake magnitudes available in the USGS CMT database. Our calculations of surface displacements indicate 1-3 millimeters could be observed across the Alaotra-Ankay rift. These values are within the observable range of precision GNSS observations, therefore our results will guide future research into the area and direct potential GNSS station installation.

  10. Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

    Science.gov (United States)

    Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

    2016-04-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

  11. Introducing Seismic Tomography with Computational Modeling

    Science.gov (United States)

    Neves, R.; Neves, M. L.; Teodoro, V.

    2011-12-01

    Learning seismic tomography principles and techniques involves advanced physical and computational knowledge. In depth learning of such computational skills is a difficult cognitive process that requires a strong background in physics, mathematics and computer programming. The corresponding learning environments and pedagogic methodologies should then involve sets of computational modelling activities with computer software systems which allow students the possibility to improve their mathematical or programming knowledge and simultaneously focus on the learning of seismic wave propagation and inverse theory. To reduce the level of cognitive opacity associated with mathematical or programming knowledge, several computer modelling systems have already been developed (Neves & Teodoro, 2010). Among such systems, Modellus is particularly well suited to achieve this goal because it is a domain general environment for explorative and expressive modelling with the following main advantages: 1) an easy and intuitive creation of mathematical models using just standard mathematical notation; 2) the simultaneous exploration of images, tables, graphs and object animations; 3) the attribution of mathematical properties expressed in the models to animated objects; and finally 4) the computation and display of mathematical quantities obtained from the analysis of images and graphs. Here we describe virtual simulations and educational exercises which enable students an easy grasp of the fundamental of seismic tomography. The simulations make the lecture more interactive and allow students the possibility to overcome their lack of advanced mathematical or programming knowledge and focus on the learning of seismological concepts and processes taking advantage of basic scientific computation methods and tools.

  12. Monitoring Instrument Performance in Regional Broadband Seismic Network Using Ambient Seismic Noise

    Science.gov (United States)

    Ye, F.; Lyu, S.; Lin, J.

    2017-12-01

    In the past ten years, the number of seismic stations has increased significantly, and regional seismic networks with advanced technology have been gradually developed all over the world. The resulting broadband data help to improve the seismological research. It is important to monitor the performance of broadband instruments in a new network in a long period of time to ensure the accuracy of seismic records. Here, we propose a method that uses ambient noise data in the period range 5-25 s to monitor instrument performance and check data quality in situ. The method is based on an analysis of amplitude and phase index parameters calculated from pairwise cross-correlations of three stations, which provides multiple references for reliable error estimates. Index parameters calculated daily during a two-year observation period are evaluated to identify stations with instrument response errors in near real time. During data processing, initial instrument responses are used in place of available instrument responses to simulate instrument response errors, which are then used to verify our results. We also examine feasibility of the tailing noise using data from stations selected from USArray in different locations and analyze the possible instrumental errors resulting in time-shifts used to verify the method. Additionally, we show an application that effects of instrument response errors that experience pole-zeros variations on monitoring temporal variations in crustal properties appear statistically significant velocity perturbation larger than the standard deviation. The results indicate that monitoring seismic instrument performance helps eliminate data pollution before analysis begins.

  13. Seismicity and seismotectonics of the Western Lake Ontario Region -relocation of the seismic events phase III

    International Nuclear Information System (INIS)

    Mohajer, A.A.

    1995-12-01

    Earthquake hazard analysis in Canada relies mainly on recorded earthquake data. The ability to record earthquakes of a given magnitude has varied considerably over time as has the accuracy of location determinations. Recomputation of earthquake locations has been suggested as a possible means of improving the existing data base for better definition of seismic sources. In this study, the locations of more than 50 small to moderate magnitude earthquakes (M≤5), in the western Lake Ontario region, were examined. Available seismograph records in the Record Centre of the National Archives of Canada were examined for events that occurred prior to 1978. The events recorded after this date showed increasing accuracy in their location determinations due to initiation and improvements of the Eastern Canada Telemetry Network (ECTN). Data compiled from the study are based on the relocated and/or selected events with the minimum travel time residuals at the Canadian and American stations. Except for a few scattered events in the south-central part of the Lake Ontario region, microearthquakes (M<3.5) cluster along or at the intersection of prominent aeromagnetic and gravity anomalies, within the Toronto-Hamilton Seismic Zone. This is indicative of certain seismotectonic relationships in this region. The depth distribution or the better located events show that a range of 5 to 20 km is dominant and, therefore, they are not near-surface stress relief phenomena. However, details of the structural manifestation of inferred seismogenic features need further ground truthing, backed by long term seismic monitoring. (author) 66 refs., 3 tabs., 6 figs

  14. Some characteristics of the seismicity of the Tyrrhenian Sea Region

    Directory of Open Access Journals (Sweden)

    P. HEDERVARI

    1974-06-01

    Full Text Available In the first p a r t of the paper the seismic strain release of the T y r r h e n i a n Sea Region (including Italy, as the function of time, is examined on the basis of t h e d a t a of the e a r t h q u a k e s t h a t took place f r om 1901.01.01 to 1970.12.31, between the northern l a t i t u d e s of 34° and 44° and between the eastern longitudes of 8° and 18.5°, respectively. All registered shocks with a R i c h t e r - m a g n i t u d e of 5.5 or over it were considered, i n d e p e n d e n t l y f r om t h e focal d e p t h . Three periods were recognized in the a c t i v i t y ; t h e lengths of which are not t h e same, however. I n the second p a r t the elastic strain release in accordance with the focal d e p t h of t h e same e a r t h q u a k e s is t r e a t e d briefly. It was found t h at t h e t o t a l strain-release had a maximum value in t h e depth between 0 and 74 kms and there was a minimum between the depth of 300 and 524 kins with an interval between 375 and 449 kms within which no earthquakes occurred at all. The general p a t t e r n of the d i s t r i b u t i o n of seismicity as t h e f u n c t i o n of hypocentral d e p t h reminds to the well-known picture, one can experience in other regions where i n t e r m e d i a t e and deep shocks occur. This s t a t e m e n t is consistent w i t h t h e idea, according to which t h e seismicity of t h e Tyrrhenian Sea Region can be discussed and explained in t h e light of t h e theory of new global tectonics. F i n a l l y , in the t h i r d p a r t of the study, the authors have s t a t e d t h at in some cases multiple events occurred b e n e a t h t h e Tyrrhenian Sea Region. Such multiple seismic events were detected in the case of other areas, such as the Fiji-Tonga-Kermadec Region, the seismic belt of South America etc., — but, according to the knowledge of t h e authors, this is t h e first occasion when multiple seismic events are

  15. Seismic Regionalization of Michoacan, Mexico and Recurrence Periods for Earthquakes

    Science.gov (United States)

    Magaña García, N.; Figueroa-Soto, Á.; Garduño-Monroy, V. H.; Zúñiga, R.

    2017-12-01

    Michoacán is one of the states with the highest occurrence of earthquakes in Mexico and it is a limit of convergence triggered by the subduction of Cocos plate over the North American plate, located in the zone of the Pacific Ocean of our country, in addition to the existence of active faults inside of the state like the Morelia-Acambay Fault System (MAFS).It is important to make a combination of seismic, paleosismological and geological studies to have good planning and development of urban complexes to mitigate disasters if destructive earthquakes appear. With statistical seismology it is possible to characterize the degree of seismic activity as well as to estimate the recurrence periods for earthquakes. For this work, seismicity catalog of Michoacán was compiled and homogenized in time and magnitude. This information was obtained from world and national agencies (SSN, CMT, etc), some data published by Mendoza and Martínez-López (2016) and starting from the seismic catalog homogenized by F. R. Zúñiga (Personal communication). From the analysis of the different focal mechanisms reported in the literature and geological studies, the seismic regionalization of the state of Michoacán complemented the one presented by Vázquez-Rosas (2012) and the recurrence periods for earthquakes within the four different seismotectonic regions. In addition, stable periods were determined for the b value of the Gutenberg-Richter (1944) using the Maximum Curvature and EMR (Entire Magnitude Range Method, 2005) techniques, which allowed us to determine recurrence periods: years for earthquakes upper to 7.5 for the subduction zone (A zone) with EMR technique and years with MAXC technique for the same years for earthquakes upper to 5 for B1 zone with EMR technique and years with MAXC technique; years for earthquakes upper to 7.0 for B2 zone with EMR technique and years with MAXC technique; and the last one, the Morelia-Acambay Fault Sistem zone (C zone) years for earthquakes

  16. Numerical Modelling of Seismic Slope Stability

    Science.gov (United States)

    Bourdeau, Céline; Havenith, Hans-Balder; Fleurisson, Jean-Alain; Grandjean, Gilles

    Earthquake ground-motions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elasto-plastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con- ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.

  17. Erosion Associated with Seismically-Induced Landslides in the Middle Longmen Shan Region, Eastern Tibetan Plateau, China

    Directory of Open Access Journals (Sweden)

    Zhikun Ren

    2017-08-01

    Full Text Available The 2008 Wenchuan earthquake and associated co-seismic landslide was the most recent expression of the rapid deformation and erosion occurring in the eastern Tibetan Plateau. The erosion associated with co-seismic landslides balances the long-term tectonic uplift in the topographic evolution of the region; however, the quantitative relationship between earthquakes, uplift, and erosion is still unknown. In order to quantitatively distinguish the seismically-induced erosion in the total erosion, here, we quantify the Wenchuan earthquake-induced erosion using the digital elevation model (DEM differential method and previously-reported landslide volumes. Our results show that the seismically-induced erosion is comparable with the pre-earthquake short-term erosion. The seismically-induced erosion rate contributes ~50% of the total erosion rate, which suggests that the local topographic evolution of the middle Longmen Shan region may be closely related to tectonic events, such as the 2008 Wenchuan earthquake. We propose that seismically-induced erosion is a very important component of the total erosion, particularly in active orogenic regions. Our results demonstrate that the remote sensing technique of differential DEM provides a powerful tool for evaluating the volume of co-seismic landslides produced in intermountain regions by strong earthquakes.

  18. Geo-Proxy-Based Site Classification for Regional Zonation of Seismic Site Effects in South Korea

    Directory of Open Access Journals (Sweden)

    Chang-Guk Sun

    2018-02-01

    Full Text Available Seismic site effects and topographic effects related to ground motion occur during an earthquake due to site-specific geotechnical or geological characteristics, including the geological or geographical structure and the characteristics of near-surface sub-soil layers. Site-specific site effects due to geological conditions have been confirmed in recent earthquake events. Earthquake-induced damage has mainly occurred at accumulated soft soil layers under basins or along coasts and rivers. An alternative method has recently been proposed for evaluating regional seismic site effects and amplification factors using digital elevation models (DEM. High-quality DEMs at high resolutions may be employed to resolve finer-scale variations in topographic gradients and consequently, correlated site response parameters. Because there are many regions in South Korea lacking borehole datasets, which are insufficient for site classification only using borehole datasets, a DEM-based proxy for seismic zonation can be effective. Thus, in this study, geo-proxy-based site classification was proposed based on empirical correlations with site response parameters and conducted for regional zonation of seismic site effects to identify the amplification of characteristics in the western metropolitan areas of South Korea, depending on the site-specific geo-spatial conditions.

  19. LITHOSPHERIC STRUCTURE OF THE CARPATHIAN-PANNONIAN REGION BASED ON THE GRAVITY MODELING BY INTEGRATING THE CELEBRATION2000 SEISMIC EXPERIMENT AND NEW GEOPHYSICAL RESULTS

    Science.gov (United States)

    Bielik, M.; Alasonati Tašárová, Z.; Zeyen, H. J.; Afonso, J.; Goetze, H.; Dérerová, J.

    2009-12-01

    Two different methods for the 3-D interpretation of the gravity field have been applied to the study of the structure and tectonics of the Carpathian-Pannonian lithosphere. The first (second) method provided a set of the different stripped gravity maps (the new lithosphere thickness map). The contribution presents the interpretation of the gravity field, which takes into account the CELEBRATION2000 seismic as well as new geophysical results. The sediment stripped gravity map is characterized by gravity minima in the Eastern Alps and Western Carpathians, and gravity maxima in the Pannonian Back-arc Basin system and the European platform. The gravity low in the Eastern Alps is produced by the thick crust (more than 45 km). The Western Carpathian gravity minimum is a result of the interference of two main gravitational effects. The first one comes from the low-density sediments of the Outer Western Carpathians and Carpathian Foredeep. The second one is due to the thick low-density upper and middle crust, reaching up to 25 km. In the Pannonian Back-arc Basin system can be observed the regional gravity high which is a result of the gravity effect of the anomalously shallow Moho. The most dominant feature of the complete 3-D stripped gravity map (crustal gravity effect map) is the abrupt change of the gravity field along the Klippen Belt zone. While the European platform is characterized by positive anomalies, the Western Carpathian orogen and the Pannonian Back-arc Basin system by relatively long-wavelength gravity low (several hundred kilometers). The lowest values are associated with the thick low-density upper and middle crust of the Inner Western Carpathians. That is why we suggest that the European Platform consists of the significantly denser crust with respect to the less dense crust of the microplates ALCAPA and Tisza-Dacia. The contrast in the gravity fields over the European platform and microplates ALCAPA and Tisza-Dacia reflect also their different crustal

  20. Study of Seismic Clusters at Bahía de Banderas Region, Mexico

    Science.gov (United States)

    Nunez-Cornu, F. J.; Rutz-Lopez, M.; Suarez-Plascencia, C.; Trejo-Gomez, E.

    2010-12-01

    Given that the coast in the states of Jalisco and south of the state of Nayarit is located within a region of high seismic potential and also because population is increasing, perhaps motivated by the development of tourism, the Civil Defense authorities of Jalisco and the Centro de Sismología y Volcanología de Occidente-SisVOc of Universidad de Guadalajara started in the year 2000 a joint project to study the seismic risk of the region, including the seismic monitoring of Colima volcano (located between the states of Jalisco and Colima). This work focuses on the study of seismicity in the area of Bahía de Banderas and northern coast of Jalisco. To this end, we perform an analysis of available seismograms to characterize active structures, their relationship to surface morphology, and possible reach of these structures into the shallow parts of the bay. The data used in this work are waveforms recorded during the year 2003 during which the seismograph network spanned the region of study. Our method is based on the identification of seismic clusters or families using cross-correlation of waveforms, earthquake relocation and modeling of fault planes. From an initial data set of 404 earthquakes located during 2003, 96 earthquakes could be related to 17 potentially active continental structures. A modeling of fault planes was possible for 11 of these structures. Subgroups of 7 structures are aligned parallel to the Middle America Trench, a possible consequence of oblique subduction. The magnitudes of earthquakes grouped into families is less than 3.6 (Ml), corresponding to fault dimensions of hundreds of meters.

  1. A preliminary regional assessment of earthquake-induced landslide susceptibility for Vrancea Seismic Region

    Science.gov (United States)

    Micu, Mihai; Balteanu, Dan; Ionescu, Constantin; Havenith, Hans; Radulian, Mircea; van Westen, Cees; Damen, Michiel; Jurchescu, Marta

    2015-04-01

    In seismically-active regions, earthquakes may trigger landslides enhancing the short-to-long term slope denudation and sediment delivery and conditioning the general landscape evolution. Co-seismic slope failures present in general a low frequency - high magnitude pattern which should be addressed accordingly by landslide hazard assessment, with respect to the generally more frequent precipitation-triggered landslides. The Vrancea Seismic Region, corresponding to the curvature sector of the Eastern Romanian Carpathians, represents the most active sub-crustal (focal depth > 50 km) earthquake province of Europe. It represents the main seismic energy source throughout Romania with significant transboundary effects recorded as far as Ukraine and Bulgaria. During the last 300 years, the region featured 14 earthquakes with M>7, among which seven events with magnitude above 7.5 and three between 7.7 and 7.9. Apart from the direct damages, the Vrancea earthquakes are also responsible for causing numerous other geohazards, such as ground fracturing, groundwater level disturbances and possible deep-seated landslide occurrences (rock slumps, rock-block slides, rock falls, rock avalanches). The older deep-seated landslides (assumed to have been) triggered by earthquakes usually affect the entire slope profile. They often formed landslide dams strongly influencing the river morphology and representing potential threats (through flash-floods) in case of lake outburst. Despite the large potential of this research issue, the correlation between the region's seismotectonic context and landslide predisposing factors has not yet been entirely understood. Presently, there is a lack of information provided by the geohazards databases of Vrancea that does not allow us to outline the seismic influence on the triggering of slope failures in this region. We only know that the morphology of numerous large, deep-seated and dormant landslides (which can possibly be reactivated in future

  2. Detection of rainfall-induced landslides on regional seismic networks

    Science.gov (United States)

    Manconi, Andrea; Coviello, Velio; Gariano, Stefano Luigi; Picozzi, Matteo

    2017-04-01

    Seismic techniques are increasingly adopted to detect signals induced by mass movements and to quantitatively evaluate geo-hydrological hazards at different spatial and temporal scales. By analyzing landslide-induced seismicity, it is possible obtaining significant information on the source of the mass wasting, as well as on its dynamics. However, currently only few studies have performed a systematic back analysis on comprehensive catalogues of events to evaluate the performance of proposed algorithms. In this work, we analyze a catalogue of 1058 landslides induced by rainfall in Italy. Among these phenomena, there are 234 rock falls, 55 debris flows, 54 mud flows, and 715 unspecified shallow landslides. This is a subset of a larger catalogue collected by the Italian research institute for geo-hydrological protection (CNR IRPI) during the period 2000-2014 (Brunetti et al., 2015). For each record, the following information are available: the type of landslide; the geographical location of the landslide (coordinates, site, municipality, province, and 3 classes of geographic accuracy); the temporal information on the landslide occurrence (day, month, year, time, date, and 3 classes of temporal accuracy); the rainfall conditions (rainfall duration and cumulated event rainfall) that have resulted in the landslide. We consider here only rainfall-induced landslides for which exact date and time were known from chronicle information. The analysis of coeval seismic data acquired by regional seismic networks show clear signals in at least 3 stations for 64 events (6% of the total dataset). Among them, 20 are associated to local earthquakes and 2 to teleseisms; 10 are anomalous signals characterized by irregular and impulsive waveforms in both time and frequency domains; 33 signals are likely associated to the landslide occurrence, as they have a cigar-shaped waveform characterized by emerging onsets, duration of several tens of seconds, and low frequencies (1-10 Hz). For

  3. Seismic rupture modelling, strong motion prediction and seismic hazard assessment: fundamental and applied approaches

    International Nuclear Information System (INIS)

    Berge-Thierry, C.

    2007-05-01

    The defence to obtain the 'Habilitation a Diriger des Recherches' is a synthesis of the research work performed since the end of my Ph D. thesis in 1997. This synthesis covers the two years as post doctoral researcher at the Bureau d'Evaluation des Risques Sismiques at the Institut de Protection (BERSSIN), and the seven consecutive years as seismologist and head of the BERSSIN team. This work and the research project are presented in the framework of the seismic risk topic, and particularly with respect to the seismic hazard assessment. Seismic risk combines seismic hazard and vulnerability. Vulnerability combines the strength of building structures and the human and economical consequences in case of structural failure. Seismic hazard is usually defined in terms of plausible seismic motion (soil acceleration or velocity) in a site for a given time period. Either for the regulatory context or the structural specificity (conventional structure or high risk construction), seismic hazard assessment needs: to identify and locate the seismic sources (zones or faults), to characterize their activity, to evaluate the seismic motion to which the structure has to resist (including the site effects). I specialized in the field of numerical strong-motion prediction using high frequency seismic sources modelling and forming part of the IRSN allowed me to rapidly working on the different tasks of seismic hazard assessment. Thanks to the expertise practice and the participation to the regulation evolution (nuclear power plants, conventional and chemical structures), I have been able to work on empirical strong-motion prediction, including site effects. Specific questions related to the interface between seismologists and structural engineers are also presented, especially the quantification of uncertainties. This is part of the research work initiated to improve the selection of the input ground motion in designing or verifying the stability of structures. (author)

  4. Numerical modeling and the physical basis of seismic discriminants

    International Nuclear Information System (INIS)

    Denny, M.D.

    1993-01-01

    Accurate seismic event discrimination is critical to detection of nuclear explosions. Numerical modeling applied to seismic event discrimination can lead to increased reliability of proliferation detection. It is particularly applicable to error budgeting and to understanding explosion and earthquake phenomenologies. There also is a need for minimum requirements to validate the models used in numerical modeling

  5. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    Science.gov (United States)

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-01-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  6. Crustal seismicity and the earthquake catalog maximum moment magnitude (Mcmax) in stable continental regions (SCRs): Correlation with the seismic velocity of the lithosphere

    Science.gov (United States)

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-12-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  7. Crustal velocity structure of central Gansu Province from regional seismic waveform inversion using firework algorithm

    Science.gov (United States)

    Chen, Yanyang; Wang, Yanbin; Zhang, Yuansheng

    2017-04-01

    The firework algorithm (FWA) is a novel swarm intelligence-based method recently proposed for the optimization of multi-parameter, nonlinear functions. Numerical waveform inversion experiments using a synthetic model show that the FWA performs well in both solution quality and efficiency. We apply the FWA in this study to crustal velocity structure inversion using regional seismic waveform data of central Gansu on the northeastern margin of the Qinghai-Tibet plateau. Seismograms recorded from the moment magnitude ( M W) 5.4 Minxian earthquake enable obtaining an average crustal velocity model for this region. We initially carried out a series of FWA robustness tests in regional waveform inversion at the same earthquake and station positions across the study region, inverting two velocity structure models, with and without a low-velocity crustal layer; the accuracy of our average inversion results and their standard deviations reveal the advantages of the FWA for the inversion of regional seismic waveforms. We applied the FWA across our study area using three component waveform data recorded by nine broadband permanent seismic stations with epicentral distances ranging between 146 and 437 km. These inversion results show that the average thickness of the crust in this region is 46.75 km, while thicknesses of the sedimentary layer, and the upper, middle, and lower crust are 3.15, 15.69, 13.08, and 14.83 km, respectively. Results also show that the P-wave velocities of these layers and the upper mantle are 4.47, 6.07, 6.12, 6.87, and 8.18 km/s, respectively.

  8. Hierarchical Bayesian Modeling of Fluid-Induced Seismicity

    Science.gov (United States)

    Broccardo, M.; Mignan, A.; Wiemer, S.; Stojadinovic, B.; Giardini, D.

    2017-11-01

    In this study, we present a Bayesian hierarchical framework to model fluid-induced seismicity. The framework is based on a nonhomogeneous Poisson process with a fluid-induced seismicity rate proportional to the rate of injected fluid. The fluid-induced seismicity rate model depends upon a set of physically meaningful parameters and has been validated for six fluid-induced case studies. In line with the vision of hierarchical Bayesian modeling, the rate parameters are considered as random variables. We develop both the Bayesian inference and updating rules, which are used to develop a probabilistic forecasting model. We tested the Basel 2006 fluid-induced seismic case study to prove that the hierarchical Bayesian model offers a suitable framework to coherently encode both epistemic uncertainty and aleatory variability. Moreover, it provides a robust and consistent short-term seismic forecasting model suitable for online risk quantification and mitigation.

  9. A Full-Wave Seismic Tomography for the Crustal Structure in the Metropolitan Beijing Region

    Science.gov (United States)

    Sun, A.; Zhao, L.; Chen, Q.

    2008-12-01

    The greater Beijing metropolitan region is located in an old cratonic block in northeast China with complex geology and several large historic earthquakes, such as the Sanhe-Pinggu earthquake (~M8.0) in 1679, the Xingtai earthquake (M7.2) in 1966, and the Tangshan earthquake (M7.8) in 1976. To enhance our understanding of the crustal structure and the seismotectonics under this region, we conduct a full-wave three-dimensional (3D) tomographic study of this region using the waveforms recorded by the newly established Beijing metropolitan digital seismic network. Since the Beijing network was put into operation in October 2001, there have been 89 local earthquakes of magnitude 3.0 and above. From these, we selected 23 events of magnitude 3.2 and above and obtained their waveform records at 50 stations within our area of interest. The types of instruments at these stations include broadband, short-period and very broadband. First-motion focal mechanisms were determined for these events. We used a regional 3D model obtained by seismic reflection surveys as the reference model and calculated the synthetic seismograms by the finite-difference method. In this first attempt at finite- frequency tomography for the Beijing region, we focus on the variation of the P-wave speed using the first- arriving P waves. We measure the frequency-dependent traveltime anomalies of the P waves by the cross- correlation between observed and synthetic P waveforms within several discrete frequency bands between 20-sec and 5-sec periods. The sensitivity or Frechet kernels of these measurements for the perturbations in P-wave speed were computed by the same finite-difference method. We will present the preliminary result in our full-wave seismic tomography for the Beijing region.

  10. Importance of modeling beam-column joints for seismic safety of reinforced concrete structures

    International Nuclear Information System (INIS)

    Sharma, Akanshu; Reddy, G.R.; Vaze, K.K.; Eligehausen, R.; Hofmann, J.

    2011-01-01

    Almost all structures, except the containment building, in a NPP can be classified as reinforced concrete (RC) framed structures. In case of such structures subjected to seismic loads, beam-column joints are recognized as the critical and vulnerable zone. During an earthquake, the global behavior of the structure is highly governed by the behavior of the joints. If the joints behave in a ductile manner, the global behavior generally will be ductile, whereas if the joints behave in a brittle fashion then the structure will display a brittle behavior. The joints of old and non-seismically detailed structures are more vulnerable and behave poorly under the earthquakes compared to the joints of new and seismically detailed structures. Modeling of these joint regions is very important for correct assessment of the seismic performance of the structures. In this paper, it is shown with the help of a recently developed joint model that not modeling the inelastic behavior of the joints can lead to significantly misleading and unsafe results in terms of the performance assessment of the structures under seismic loads. Comparison of analytical and experimental results is shown for two structures, tested under lateral monotonic seismic pushover loads. It is displayed that the model can predict the inelastic seismic response of structures considering joint distortion with high accuracy by little extra effort in modeling. (author)

  11. Global and Regional 3D Tomography for Improved Seismic Event Location and Uncertainty in Explosion Monitoring

    Science.gov (United States)

    Downey, N.; Begnaud, M. L.; Hipp, J. R.; Ballard, S.; Young, C. S.; Encarnacao, A. V.

    2017-12-01

    The SALSA3D global 3D velocity model of the Earth was developed to improve the accuracy and precision of seismic travel time predictions for a wide suite of regional and teleseismic phases. Recently, the global SALSA3D model was updated to include additional body wave phases including mantle phases, core phases, reflections off the core-mantle boundary and underside reflections off the surface of the Earth. We show that this update improves travel time predictions and leads directly to significant improvements in the accuracy and precision of seismic event locations as compared to locations computed using standard 1D velocity models like ak135, or 2½D models like RSTT. A key feature of our inversions is that path-specific model uncertainty of travel time predictions are calculated using the full 3D model covariance matrix computed during tomography, which results in more realistic uncertainty ellipses that directly reflect tomographic data coverage. Application of this method can also be done at a regional scale: we present a velocity model with uncertainty obtained using data obtained from the University of Utah Seismograph Stations. These results show a reduction in travel-time residuals for re-located events compared with those obtained using previously published models.

  12. From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle

    Science.gov (United States)

    Avouac, Jean-Philippe

    2015-05-01

    Understanding the partitioning of seismic and aseismic fault slip is central to seismotectonics as it ultimately determines the seismic potential of faults. Thanks to advances in tectonic geodesy, it is now possible to develop kinematic models of the spatiotemporal evolution of slip over the seismic cycle and to determine the budget of seismic and aseismic slip. Studies of subduction zones and continental faults have shown that aseismic creep is common and sometimes prevalent within the seismogenic depth range. Interseismic coupling is generally observed to be spatially heterogeneous, defining locked patches of stress accumulation, to be released in future earthquakes or aseismic transients, surrounded by creeping areas. Clay-rich tectonites, high temperature, and elevated pore-fluid pressure seem to be key factors promoting aseismic creep. The generally logarithmic time evolution of afterslip is a distinctive feature of creeping faults that suggests a logarithmic dependency of fault friction on slip rate, as observed in laboratory friction experiments. Most faults can be considered to be paved with interlaced patches where the friction law is either rate-strengthening, inhibiting seismic rupture propagation, or rate-weakening, allowing for earthquake nucleation. The rate-weakening patches act as asperities on which stress builds up in the interseismic period; they might rupture collectively in a variety of ways. The pattern of interseismic coupling can help constrain the return period of the maximum- magnitude earthquake based on the requirement that seismic and aseismic slip sum to match long-term slip. Dynamic models of the seismic cycle based on this conceptual model can be tuned to reproduce geodetic and seismological observations. The promise and pitfalls of using such models to assess seismic hazard are discussed.

  13. Seismic Energy Generation and Partitioning into Various Regional Phases from Different Seismic Sources in the Middle East Region

    Science.gov (United States)

    2007-09-20

    a), a 3C SP seismic station (b) and a sensor BlastMateIII, Oron quarry (c)............................... 9 Figure 7. Seismic Array MMAI (AS49) of... seismic stations of Jordan network at distance range 22-285 km (a), and at IMS array MMAI (AS49) at 350 km, BP filtered 2-8 Hz (b...sites and portable stations, inserts show detailed location of the tripartite array elements (st.6) and configuration of the explosion boreholes and

  14. Motorized Activity on Legacy Seismic Lines: A Predictive Modeling Approach to Prioritize Restoration Efforts.

    Science.gov (United States)

    Hornseth, M L; Pigeon, K E; MacNearney, D; Larsen, T A; Stenhouse, G; Cranston, J; Finnegan, L

    2018-05-11

    Natural regeneration of seismic lines, cleared for hydrocarbon exploration, is slow and often hindered by vegetation damage, soil compaction, and motorized human activity. There is an extensive network of seismic lines in western Canada which is known to impact forest ecosystems, and seismic lines have been linked to declines in woodland caribou (Rangifer tarandus caribou). Seismic line restoration is costly, but necessary for caribou conservation to reduce cumulative disturbance. Understanding where motorized activity may be impeding regeneration of seismic lines will aid in prioritizing restoration. Our study area in west-central Alberta, encompassed five caribou ranges where restoration is required under federal species at risk recovery strategies, hence prioritizing seismic lines for restoration is of immediate conservation value. To understand patterns of motorized activity on seismic lines, we evaluated five a priori hypotheses using a predictive modeling framework and Geographic Information System variables across three landscapes in the foothills and northern boreal regions of Alberta. In the northern boreal landscape, motorized activity was most common in dry areas with a large industrial footprint. In highly disturbed areas of the foothills, motorized activity on seismic lines increased with low vegetation heights, relatively dry soils, and further from forest cutblocks, while in less disturbed areas of the foothills, motorized activity on seismic lines decreased proportional to seismic line density, slope steepness, and white-tailed deer abundance, and increased proportional with distance to roads. We generated predictive maps of high motorized activity, identifying 21,777 km of seismic lines where active restoration could expedite forest regeneration.

  15. Source characterization and dynamic fault modeling of induced seismicity

    Science.gov (United States)

    Lui, S. K. Y.; Young, R. P.

    2017-12-01

    In recent years there are increasing concerns worldwide that industrial activities in the sub-surface can cause or trigger damaging earthquakes. In order to effectively mitigate the damaging effects of induced seismicity, the key is to better understand the source physics of induced earthquakes, which still remain elusive at present. Furthermore, an improved understanding of induced earthquake physics is pivotal to assess large-magnitude earthquake triggering. A better quantification of the possible causes of induced earthquakes can be achieved through numerical simulations. The fault model used in this study is governed by the empirically-derived rate-and-state friction laws, featuring a velocity-weakening (VW) patch embedded into a large velocity-strengthening (VS) region. Outside of that, the fault is slipping at the background loading rate. The model is fully dynamic, with all wave effects resolved, and is able to resolve spontaneous long-term slip history on a fault segment at all stages of seismic cycles. An earlier study using this model has established that aseismic slip plays a major role in the triggering of small repeating earthquakes. This study presents a series of cases with earthquakes occurring on faults with different fault frictional properties and fluid-induced stress perturbations. The effects to both the overall seismicity rate and fault slip behavior are investigated, and the causal relationship between the pre-slip pattern prior to the event and the induced source characteristics is discussed. Based on simulation results, the subsequent step is to select specific cases for laboratory experiments which allow well controlled variables and fault parameters. Ultimately, the aim is to provide better constraints on important parameters for induced earthquakes based on numerical modeling and laboratory data, and hence to contribute to a physics-based induced earthquake hazard assessment.

  16. In-situ measurements of seismic velocities in the San Francisco Bay region...part II

    Science.gov (United States)

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.

    1976-01-01

    Seismic wave velocities (compressional and shear) are important parameters for determining the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. Currently a program is in progress to measure seismic velocities in the San Francisco Bay region at an estimated 150 sites. At each site seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill hole cuttings, undisturbed samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the site. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. The broad data base available in the San Francisco Bay region suggests using the area as a pilot area for the development of general techniques applicable to other areas.

  17. Modeling the impact of melt on seismic properties during mountain building

    Science.gov (United States)

    Lee, Amicia L.; Walker, Andrew M.; Lloyd, Geoffrey E.; Torvela, Taija

    2017-03-01

    Initiation of partial melting in the mid/lower crust causes a decrease in P wave and S wave velocities; recent studies imply that the relationship between these velocities and melt is not simple. We have developed a modeling approach to assess the combined impact of various melt and solid phase properties on seismic velocities and anisotropy. The modeling is based on crystallographic preferred orientation (CPO) data measured from migmatite samples, allowing quantification of the variation of seismic velocities with varying melt volumes, shapes, orientations, and matrix anisotropy. The results show nonlinear behavior of seismic properties as a result of the interaction of all of these physical properties, which in turn depend on lithology, stress regime, strain rate, preexisting rock fabrics, and pressure-temperature conditions. This nonlinear behavior is evident when applied to a suite of samples from a traverse across a migmatitic shear zone in the Seiland Igneous Province, Northern Norway. Critically, changes in solid phase composition and CPO, and melt shape and orientation with respect to the wave propagation direction can result in huge variations in the same seismic property even if the melt fraction remains the same. A comparison with surface wave interpretations from tectonically active regions highlights the issues in current models used to predict melt percentages or partially molten regions. Interpretation of seismic data to infer melt percentages or extent of melting should, therefore, always be underpinned by robust modeling of the underlying geological parameters combined with examination of multiple seismic properties in order to reduce uncertainty of the interpretation.

  18. Source modelling in seismic risk analysis for nuclear power plants

    International Nuclear Information System (INIS)

    Yucemen, M.S.

    1978-12-01

    The proposed probabilistic procedure provides a consistent method for the modelling, analysis and updating of uncertainties that are involved in the seismic risk analysis for nuclear power plants. The potential earthquake activity zones are idealized as point, line or area sources. For these seismic source types, expressions to evaluate their contribution to seismic risk are derived, considering all the possible site-source configurations. The seismic risk at a site is found to depend not only on the inherent randomness of the earthquake occurrences with respect to magnitude, time and space, but also on the uncertainties associated with the predicted values of the seismic and geometric parameters, as well as the uncertainty in the attenuation model. The uncertainty due to the attenuation equation is incorporated into the analysis through the use of random correction factors. The influence of the uncertainty resulting from the insufficient information on the seismic parameters and source geometry is introduced into the analysis by computing a mean risk curve averaged over the various alternative assumptions on the parameters and source geometry. Seismic risk analysis is carried for the city of Denizli, which is located in the seismically most active zone of Turkey. The second analysis is for Akkuyu

  19. Region-specific deterministic and probabilistic seismic hazard ...

    Indian Academy of Sciences (India)

    3National Research Institute of Astronomy and Geophysics (NRIAG), Cairo 11421, Egypt. ∗ ... were assigned to different Mmax values and the selected GMPE to calculate the final hazard ... zone is considered as a prominent seismic gap and.

  20. 2D and 3D numerical modeling of seismic waves from explosion sources

    International Nuclear Information System (INIS)

    McLaughlin, K.L.; Stevens, J.L.; Barker, T.G.; Shkoller, B.; Day, S.M.

    1993-01-01

    Over the last decade, nonlinear and linear 2D axisymmetric finite difference codes have been used in conjunction with far-field seismic Green's functions to simulate seismic waves from a variety of sources. In this paper we briefly review some of the results and conclusions that have resulted from numerical simulations and explosion modeling in support of treaty verification research at S-CUBED in the last decade. We then describe in more detail the results from two recent projects. Our goal is to provide a flavor for the kinds of problems that can be examined with numerical methods for modeling excitation of seismic waves from explosions. Two classes of problems have been addressed; nonlinear and linear near-source interactions. In both classes of problems displacements and tractions are saved on a closed surface in the linear region and the representation theorem is used to propagate the seismic waves to the far-field

  1. An Assessment of the Seismicity of the Bursa Region from a Temporary Seismic Network

    Science.gov (United States)

    Gok, Elcin; Polat, Orhan

    2012-04-01

    A temporary earthquake station network of 11 seismological recorders was operated in the Bursa region, south of the Marmara Sea in the northwest of Turkey, which is located at the southern strand of the North Anatolian Fault Zone (NAFZ). We located 384 earthquakes out of a total of 582 recorded events that span the study area between 28.50-30.00°E longitudes and 39.75-40.75°N latitudes. The depth of most events was found to be less than 29 km, and the magnitude interval ranges were between 0.3 ≤ ML ≤ 5.4, with RMS less than or equal to 0.2. Seismic activities were concentrated southeast of Uludag Mountain (UM), in the Kestel-Igdir area and along the Gemlik Fault (GF). In the study, we computed 10 focal mechanisms from temporary and permanents networks. The predominant feature of the computed focal mechanisms is the relatively widespread near horizontal northwest-southeast (NW-SE) T-axis orientation. These fault planes have been used to obtain the orientation and shape factor (R, magnitude stress ratio) of the principal stress tensors (σ1, σ2, σ3). The resulting stress tensors reveal σ1 closer to the vertical (oriented NE-SW) and σ2, σ3 horizontal with R = 0.5. These results confirm that Bursa and its vicinity could be defined by an extensional regime showing a primarily normal to oblique-slip motion character. It differs from what might be expected from the stress tensor inversion for the NAFZ. Different fault patterns related to structural heterogeneity from the north to the south in the study area caused a change in the stress regime from strike-slip to normal faulting.

  2. Full Seismic Waveform Tomography of the Japan region using Adjoint Methods

    Science.gov (United States)

    Steptoe, Hamish; Fichtner, Andreas; Rickers, Florian; Trampert, Jeannot

    2013-04-01

    We present a full-waveform tomographic model of the Japan region based on spectral-element wave propagation, adjoint techniques and seismic data from dense station networks. This model is intended to further our understanding of both the complex regional tectonics and the finite rupture processes of large earthquakes. The shallow Earth structure of the Japan region has been the subject of considerable tomographic investigation. The islands of Japan exist in an area of significant plate complexity: subduction related to the Pacific and Philippine Sea plates is responsible for the majority of seismicity and volcanism of Japan, whilst smaller micro-plates in the region, including the Okhotsk, and Okinawa and Amur, part of the larger North America and Eurasia plates respectively, contribute significant local intricacy. In response to the need to monitor and understand the motion of these plates and their associated faults, numerous seismograph networks have been established, including the 768 station high-sensitivity Hi-net network, 84 station broadband F-net and the strong-motion seismograph networks K-net and KiK-net in Japan. We also include the 55 station BATS network of Taiwan. We use this exceptional coverage to construct a high-resolution model of the Japan region from the full-waveform inversion of over 15,000 individual component seismograms from 53 events that occurred between 1997 and 2012. We model these data using spectral-element simulations of seismic wave propagation at a regional scale over an area from 120°-150°E and 20°-50°N to a depth of around 500 km. We quantify differences between observed and synthetic waveforms using time-frequency misfits allowing us to separate both phase and amplitude measurements whilst exploiting the complete waveform at periods of 15-60 seconds. Fréchet kernels for these misfits are calculated via the adjoint method and subsequently used in an iterative non-linear conjugate-gradient optimization. Finally, we employ

  3. Technical Seismicity as Natural Extreme in Karviná Region

    Czech Academy of Sciences Publication Activity Database

    Kaláb, Zdeněk; Kořínek, R.; Hrubešová, E.

    2009-01-01

    Roč. 4, 2a (2009), s. 87-94 ISSN 1896-3145. [Ochrona środowiska w górnictwie podziemnym, odkrywkowym i otworowym. Bochnia, 20.05.2009-22.05.2009] Grant - others:GA ČR(CZ) GA103/09/2007 Institutional research plan: CEZ:AV0Z30860518 Keywords : mining induced seismicity * seismic loading Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  4. Background noise model development for seismic stations of KMA

    Science.gov (United States)

    Jeon, Youngsoo

    2010-05-01

    The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

  5. A Comparison of the Crustal Deformation Predicted by Glacial Isostatic Adjustment to Seismicity in the Baffin Region of Northern Canada

    Science.gov (United States)

    James, T. S.; Schamehorn, T.; Bent, A. L.; Allen, T. I.; Mulder, T.; Simon, K.

    2016-12-01

    The horizontal crustal strain-rates induced by glacial isostatic adjustment (GIA) in northern Canada and western Greenland region are compared to the spatial pattern of seismicity. For the comparison, an updated seismicity catalogue was created from the 2010 version of the NRCan Seismic Hazard Earthquake Epicentre File (SHEEF2010) catalogue and the Greenland Ice Sheet Monitoring Network (GLISN) catalogue of the Geological Survey of Denmark and Greenland (GEUS). Crustal motion rates were computed with the Innu/Laur16 ice-sheet history and the VM5a viscosity profile (Simon et al., 2015; 2016). This GIA model optimizes the fit to relative sea-level and vertical crustal motion measurements around Hudson Bay and in the Canadian Arctic Archipelago (CAA). A region in Baffin Bay with historically high seismicity, including the 1933 M 7.4 and the 1934 and 1945 M 6.5 earthquakes, features high predicted GIA strain-rates. Elsewhere, agreement is not strong, with zones of seismicity occurring where predicted horizontal crustal strain-rates are small and large crustal strain-rates predicted where earthquake occurrence is muted. For example, large compressional crustal strain-rates are predicted beneath seismically quiescent portions of the Greenland ice sheet. Similarly, large predicted extensional strain-rates occur around southern Hudson Bay and the Foxe Basin, which are also regions of relative seismic quiescence. Additional factors to be considered include the orientation of the background stress field, relative to the predicted stress changes, and potential pre-existing zones of lithospheric weakness.

  6. Homogenization of Electromagnetic and Seismic Wavefields for Joint Inverse Modeling

    Science.gov (United States)

    Newman, G. A.; Commer, M.; Petrov, P.; Um, E. S.

    2011-12-01

    A significant obstacle in developing a robust joint imaging technology exploiting seismic and electromagnetic (EM) wave fields is the resolution at which these different geophysical measurements sense the subsurface. Imaging of seismic reflection data is an order of magnitude finer in resolution and scale compared to images produced with EM data. A consistent joint image of the subsurface geophysical attributes (velocity, electrical conductivity) requires/demands the different geophysical data types be similar in their resolution of the subsurface. The superior resolution of seismic data results from the fact that the energy propagates as a wave, while propagation of EM energy is diffusive and attenuates with distance. On the other hand, the complexity of the seismic wave field can be a significant problem due to high reflectivity of the subsurface and the generation of multiple scattering events. While seismic wave fields have been very useful in mapping the subsurface for energy resources, too much scattering and too many reflections can lead to difficulties in imaging and interpreting seismic data. To overcome these obstacles a formulation for joint imaging of seismic and EM wave fields is introduced, where each data type is matched in resolution. In order to accomplish this, seismic data are first transformed into the Laplace-Fourier Domain, which changes the modeling of the seismic wave field from wave propagation to diffusion. Though high frequency information (reflectivity) is lost with this transformation, several benefits follow: (1) seismic and EM data can be easily matched in resolution, governed by the same physics of diffusion, (2) standard least squares inversion works well with diffusive type problems including both transformed seismic and EM, (3) joint imaging of seismic and EM data may produce better starting velocity models critical for successful reverse time migration or full waveform imaging of seismic data (non transformed) and (4

  7. Probabilistic modeling of caprock leakage from seismic reflection data

    DEFF Research Database (Denmark)

    Zunino, Andrea; Hansen, Thomas Mejer; Bergjofd-Kitterød, Ingjerd

    We illustrate a methodology which helps to perform a leakage risk analysis for a CO2 reservoir based on a consistent, probabilistic approach to geophysical and geostatistical inversion. Generally, risk assessments of storage complexes are based on geological models and simulations of CO2 movement...... within the storage complexes. The geological models are built on top of geophysical data such as seismic surveys, geological information and well logs from the reservoir or nearby regions. The risk assessment of CO2 storage requires a careful analysis which accounts for all sources of uncertainty....... However, at present, no well-defined and consistent method for mapping the true uncertainty related to the geophysical data and how that uncertainty affects the overall risk assessment for the potential storage site is available. To properly quantify the uncertainties and to avoid unrealistic...

  8. HRM: HII Region Models

    Science.gov (United States)

    Wenger, Trey V.; Kepley, Amanda K.; Balser, Dana S.

    2017-07-01

    HII Region Models fits HII region models to observed radio recombination line and radio continuum data. The algorithm includes the calculations of departure coefficients to correct for non-LTE effects. HII Region Models has been used to model star formation in the nucleus of IC 342.

  9. Seismically integrated geologic modelling: Guntong Field, Malay Basin

    Energy Technology Data Exchange (ETDEWEB)

    Calvert, Craig S.; Bhuyan, K.; Sterling, J. Helwick; Hill, Rob E.; Hubbard, R. Scott; Khare, Vijay; Wahrmund, Leslie A.; Wang, Gann-Shyong

    1998-12-31

    This presentation relates to a research project on offshore seismically reservoir modelling. The goal of the project was to develop and test a process for interpreting reservoir properties from 3-D seismic data and for integrating these data into the building of 3-D geologic models that would be suitable for use in flow simulation studies. The project produced a 3-D geologic model for three reservoir intervals and three predominantly non-reservoir intervals. Each reservoir interval was subdivided into faces that were determined by integrating core, well log, and seismic interpretations. predictions of porosity and lithology used in building the geologic model were made using seismic attributes calculated from acoustic impedance data. 8 figs.

  10. Seismic model of the nuclear boiler SPX2

    International Nuclear Information System (INIS)

    Christodoulou, K.

    1982-01-01

    A model of the nuclear boiler SPX2 is proposed in this paper enabling to carry out comparative calculations on the response to seismic effects. The calculations are made in CISE and SEPTEN departments of Electricite de France [fr

  11. Seismic hazard and seismic risk assessment based on the unified scaling law for earthquakes: Himalayas and adjacent regions

    Science.gov (United States)

    Nekrasova, A. K.; Kossobokov, V. G.; Parvez, I. A.

    2015-03-01

    For the Himalayas and neighboring regions, the maps of seismic hazard and seismic risk are constructed with the use of the estimates for the parameters of the unified scaling law for earthquakes (USLE), in which the Gutenberg-Richter law for magnitude distribution of seismic events within a given area is applied in the modified version with allowance for linear dimensions of the area, namely, log N( M, L) = A + B (5 - M) + C log L, where N( M, L) is the expected annual number of the earthquakes with magnitude M in the area with linear dimension L. The spatial variations in the parameters A, B, and C for the Himalayas and adjacent regions are studied on two time intervals from 1965 to 2011 and from 1980 to 2011. The difference in A, B, and C between these two time intervals indicates that seismic activity experiences significant variations on a scale of a few decades. With a global consideration of the seismic belts of the Earth overall, the estimates of coefficient A, which determines the logarithm of the annual average frequency of the earthquakes with a magnitude of 5.0 and higher in the zone with a linear dimension of 1 degree of the Earth's meridian, differ by a factor of 30 and more and mainly fall in the interval from -1.1 to 0.5. The values of coefficient B, which describes the balance between the number of earthquakes with different magnitudes, gravitate to 0.9 and range from less than 0.6 to 1.1 and higher. The values of coefficient C, which estimates the fractal dimension of the local distribution of epicenters, vary from 0.5 to 1.4 and higher. In the Himalayas and neighboring regions, the USLE coefficients mainly fall in the intervals of -1.1 to 0.3 for A, 0.8 to 1.3 for B, and 1.0 to 1.4 for C. The calculations of the local value of the expected peak ground acceleration (PGA) from the maximal expected magnitude provided the necessary basis for mapping the seismic hazards in the studied region. When doing this, we used the local estimates of the

  12. Epicenter Location of Regional Seismic Events Using Love Wave and Rayleigh Wave Ambient Seismic Noise Green's Functions

    Science.gov (United States)

    Levshin, A. L.; Barmin, M. P.; Moschetti, M. P.; Mendoza, C.; Ritzwoller, M. H.

    2011-12-01

    We describe a novel method to locate regional seismic events based on exploiting Empirical Green's Functions (EGF) that are produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long time-series of ambient noise recorded at the two stations. The EGFs principally contain Rayleigh waves on the vertical-vertical cross-correlations and Love waves on the transverse-transverse cross-correlations. Earlier work (Barmin et al., "Epicentral location based on Rayleigh wave empirical Green's functions from ambient seismic noise", Geophys. J. Int., 2011) showed that group time delays observed on Rayleigh wave EGFs can be exploited to locate to within about 1 km moderate sized earthquakes using USArray Transportable Array (TA) stations. The principal advantage of the method is that the ambient noise EGFs are affected by lateral variations in structure similarly to the earthquake signals, so the location is largely unbiased by 3-D structure. However, locations based on Rayleigh waves alone may be biased by more than 1 km if the earthquake depth is unknown but lies between 2 km and 7 km. This presentation is motivated by the fact that group time delays for Love waves are much less affected by earthquake depth than Rayleigh waves; thus exploitation of Love wave EGFs may reduce location bias caused by uncertainty in event depth. The advantage of Love waves to locate seismic events, however, is mitigated by the fact that Love wave EGFs have a smaller SNR than Rayleigh waves. Here, we test the use of Love and Rayleigh wave EGFs between 5- and 15-sec period to locate seismic events based on the USArray TA in the western US. We focus on locating aftershocks of the 2008 M 6.0 Wells earthquake, mining blasts in Wyoming and Montana, and small earthquakes near Norman, OK and Dallas, TX, some of which may be triggered by hydrofracking or injection wells.

  13. Mean vertically inhomogeneous models of the uppermost crust along seismic profiles in the Ohře rift and Moravo-Silesian region

    Czech Academy of Sciences Publication Activity Database

    Holub, Karel; Málek, J.; Novotný, O.; Rušajová, Jana; Valenta, J.

    2006-01-01

    Roč. 6, č. 2 (2006), s. 125-131 ISSN 1213-1962. [Nové poznatky a měření v seismologii, inženýrské geofyzice a geotechnice/15./. Ostrava, 11.04.2006-13.04.2006] R&D Projects: GA ČR GA205/03/0999; GA AV ČR IAA300460602 Institutional research plan: CEZ:AV0Z30860518 Keywords : refraction measurement, * vertically inhomogeneous models, * Weichert-Herglotz method Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  14. Regional seismic lines reprocessed using post-stack processing techniques; National Petroleum Reserve, Alaska

    Science.gov (United States)

    Miller, John J.; Agena, W.F.; Lee, M.W.; Zihlman, F.N.; Grow, J.A.; Taylor, D.J.; Killgore, Michele; Oliver, H.L.

    2000-01-01

    This CD-ROM contains stacked, migrated, 2-Dimensional seismic reflection data and associated support information for 22 regional seismic lines (3,470 line-miles) recorded in the National Petroleum Reserve ? Alaska (NPRA) from 1974 through 1981. Together, these lines constitute about one-quarter of the seismic data collected as part of the Federal Government?s program to evaluate the petroleum potential of the Reserve. The regional lines, which form a grid covering the entire NPRA, were created by combining various individual lines recorded in different years using different recording parameters. These data were reprocessed by the USGS using modern, post-stack processing techniques, to create a data set suitable for interpretation on interactive seismic interpretation computer workstations. Reprocessing was done in support of ongoing petroleum resource studies by the USGS Energy Program. The CD-ROM contains the following files: 1) 22 files containing the digital seismic data in standard, SEG-Y format; 2) 1 file containing navigation data for the 22 lines in standard SEG-P1 format; 3) 22 small scale graphic images of each seismic line in Adobe Acrobat? PDF format; 4) a graphic image of the location map, generated from the navigation file, with hyperlinks to the graphic images of the seismic lines; 5) an ASCII text file with cross-reference information for relating the sequential trace numbers on each regional line to the line number and shotpoint number of the original component lines; and 6) an explanation of the processing used to create the final seismic sections (this document). The SEG-Y format seismic files and SEG-P1 format navigation file contain all the information necessary for loading the data onto a seismic interpretation workstation.

  15. Automated seismic detection of landslides at regional scales: a Random Forest based detection algorithm

    Science.gov (United States)

    Hibert, C.; Michéa, D.; Provost, F.; Malet, J. P.; Geertsema, M.

    2017-12-01

    Detection of landslide occurrences and measurement of their dynamics properties during run-out is a high research priority but a logistical and technical challenge. Seismology has started to help in several important ways. Taking advantage of the densification of global, regional and local networks of broadband seismic stations, recent advances now permit the seismic detection and location of landslides in near-real-time. This seismic detection could potentially greatly increase the spatio-temporal resolution at which we study landslides triggering, which is critical to better understand the influence of external forcings such as rainfalls and earthquakes. However, detecting automatically seismic signals generated by landslides still represents a challenge, especially for events with small mass. The low signal-to-noise ratio classically observed for landslide-generated seismic signals and the difficulty to discriminate these signals from those generated by regional earthquakes or anthropogenic and natural noises are some of the obstacles that have to be circumvented. We present a new method for automatically constructing instrumental landslide catalogues from continuous seismic data. We developed a robust and versatile solution, which can be implemented in any context where a seismic detection of landslides or other mass movements is relevant. The method is based on a spectral detection of the seismic signals and the identification of the sources with a Random Forest machine learning algorithm. The spectral detection allows detecting signals with low signal-to-noise ratio, while the Random Forest algorithm achieve a high rate of positive identification of the seismic signals generated by landslides and other seismic sources. The processing chain is implemented to work in a High Performance Computers centre which permits to explore years of continuous seismic data rapidly. We present here the preliminary results of the application of this processing chain for years

  16. Seismic modelling of coal bed methane strata, Willow Creek, Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, S.E.; Mayer, R.; Lawton, D.C.; Langenberg, W. [Consortium for Research in Elastic Wave Exploration Seismology, Calgary, AB (Canada)

    2001-07-01

    The purpose is to determine the feasibility of applying high- resolution reflection seismic surveying to coalbed methane (CBM) exploration and development. Numerical reflection seismic methods are examined for measuring the mapping continuity and coherence of coal zones. Numerical modelling of a coal zone in Upper Cretaceous sediments near Willow Creek, Alberta indicates that seismic data that is predominantly of 100 Hz is required to map the coal zone and lateral facies variations within the deposit. For resolution of individual coal seams, a central frequency >150 Hz would be needed. 26 refs., 17 figs., 3 tabs.

  17. The attenuation of seismic intensity in the Etna region and comparison with other Italian volcanic districts

    Directory of Open Access Journals (Sweden)

    T. Tuvè

    2006-06-01

    Full Text Available A detailed analysis of the intensity attenuation in the Etna and other Italian volcanic districts, was performed using the most recent and complete intensity datasets. Attenuation laws were derived through empirical models fitting ?I (the difference between epicentral I0 and site Ix intensities average values versus hypocentral site distances by the least-square method. The huge amount of data available for the Etna area allowed us to elaborate bi-linear and logarithmic attenuation models, also taking source effects into account. Furthermore, the coefficients of the Grandori formulation have been re-calculated to verify the ones previously defined for seismic hazard purposes. Among the tested relationships, the logarithmic one is simple and fairly stable, so it was also adopted for the other volcanic Italian areas. The analysis showed different attenuation trends: on the one hand, Etna and Ischia show the highest decay of intensity (?I=4 in the first 20 km; on the contrary, the Aeolian Islands and Albani Hills present a slight intensity attenuation (?I=2 at 20 km from the hypocentre; finally, Vesuvius seems to have an intermediate behaviour between the two groups. The proposed regionalization gives a significantly better image of near-field damage in volcanic regions and is easily applicable to probabilistic seismic hazard analyses.

  18. False alarms and mine seismicity: An example from the Gentry Mountain mining region, Utah. Los Alamos Source Region Project

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, S.R.

    1992-09-23

    Mining regions are a cause of concern for monitoring of nuclear test ban treaties because they present the opportunity for clandestine nuclear tests (i.e. decoupled explosions). Mining operations are often characterized by high seismicity rates and can provide the cover for excavating voids for decoupling. Chemical explosions (seemingly as part of normal mining activities) can be used to complicate the signals from a simultaneous decoupled nuclear explosion. Thus, most concern about mines has dealt with the issue of missed violations to a test ban treaty. In this study, we raise the diplomatic concern of false alarms associated with mining activities. Numerous reports and papers have been published about anomalous seismicity associated with mining activities. As part of a large discrimination study in the western US (Taylor et al., 1989), we had one earthquake that was consistently classified as an explosion. The magnitude 3.5 disturbance occurred on May 14, 1981 and was conspicuous in its lack of Love waves, relative lack of high- frequency energy, low Lg/Pg ratio, and high m{sub b} {minus} M{sub s}. A moment-tensor solution by Patton and Zandt (1991) indicated the event had a large implosional component. The event occurred in the Gentry Mountain coal mining region in the eastern Wasatch Plateau, Utah. Using a simple source representation, we modeled the event as a tabular excavation collapse that occurred as a result of normal mining activities. This study raises the importance of having a good catalogue of seismic data and information about mining activities from potential proliferant nations.

  19. Application of probabilistic seismic hazard models with special calculation for the waste storage sites in Egypt

    International Nuclear Information System (INIS)

    Othman, A.A.; El-Hemamy, S.T.

    2000-01-01

    Probabilistic strong motion maps of Egypt are derived by applying Gumbel models and likelihood method to 8 earthquake source zones in Egypt and adjacent regions. Peak horizontal acceleration is mapped. Seismic data are collected from Helwan Catalog (1900-1997), regional catalog of earthquakes from the International Seismological Center (ISC,1910-1993) and earthquake data reports of US Department of International Geological Survey (USCGS, 1900-1994). Iso-seismic maps are also available for some events, which occurred in Egypt. Some earthquake source zones are well defined on the basis of both tectonics and average seismicity rates, but a lack of understanding of the near field effects of the large earthquakes prohibits accurate estimates of ground motion in their vicinity. Some source zones have no large-scale crustal features or zones of weakness that can explain the seismicity and must, therefore, be defined simply as concentrations of seismic activity with no geological or geophysical controls on the boundaries. Other source zones lack information on low-magnitude seismicity that would be representative of longer periods of time. Comparisons of the new probabilistic ground motion estimates in Egypt with equivalent estimates made in 1990 have been done. The new ground motion estimates are used to produce a new peak ground acceleration map to replace the 1990 peak acceleration zoning maps in the Building code of Egypt. (author)

  20. Propagation of Regional Seismic Phases in Western Europe

    Science.gov (United States)

    1991-03-08

    and Southeastern France recorded at short period stations of the LDG (Laboratoire de Detection Geophysique , France) and IGG (Istituto Geofisico di...here were provided by the L.D.G. (Laboratoire de Geophysique ). The french seismic network consists of 27 stations with the same features : the

  1. Regional Seismic Arrays and Nuclear Test Ban Verification

    Science.gov (United States)

    1990-12-01

    Anderson, K. R., S. T. Rosenberg, and D. Lanan (1982). Automatic association using expert system techniq:_,s, in Seismic Discrimination, Semiannual...Travel Times, Earthquake, by Glenn D. Nelson and John E. V idale . ........... ...................................... ............ . ....... 395 Lund...1553 Nelson, Glenn D. and John E. Vidale-Earthquake Locations by 3-D Finite Difference Travel Times

  2. Mechanical System Simulations for Seismic Signature Modeling

    National Research Council Canada - National Science Library

    Lacombe, J

    2001-01-01

    .... Results for an M1A1 and T72 are discussed. By analyzing the simulated seismic signature data in conjunction with the spectral features associated with the vibrations of specific vehicle sprung and un-sprung components we are able to make...

  3. False alarms and mine seismicity: An example from the Gentry Mountain mining region, Utah

    International Nuclear Information System (INIS)

    Taylor, S.R.

    1992-01-01

    Mining regions are a cause of concern for monitoring of nuclear test ban treaties because they present the opportunity for clandestine nuclear tests (i.e. decoupled explosions). Mining operations are often characterized by high seismicity rates and can provide the cover for excavating voids for decoupling. Chemical explosions (seemingly as part of normal mining activities) can be used to complicate the signals from a simultaneous decoupled nuclear explosion. Thus, most concern about mines has dealt with the issue of missed violations to a test ban treaty. In this study, we raise the diplomatic concern of false alarms associated with mining activities. Numerous reports and papers have been published about anomalous seismicity associated with mining activities. As part of a large discrimination study in the western US (Taylor et al., 1989), we had one earthquake that was consistently classified as an explosion. The magnitude 3.5 disturbance occurred on May 14, 1981 and was conspicuous in its lack of Love waves, relative lack of high- frequency energy, low Lg/Pg ratio, and high m b - M s . A moment-tensor solution by Patton and Zandt (1991) indicated the event had a large implosional component. The event occurred in the Gentry Mountain coal mining region in the eastern Wasatch Plateau, Utah. Using a simple source representation, we modeled the event as a tabular excavation collapse that occurred as a result of normal mining activities. This study raises the importance of having a good catalogue of seismic data and information about mining activities from potential proliferant nations

  4. Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

    Science.gov (United States)

    McGuire, Jeffrey J.; Lohman, Rowena B.; Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.

    2015-01-01

    The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from

  5. Present-Day Mars' Seismicity Predicted From 3-D Thermal Evolution Models of Interior Dynamics

    Science.gov (United States)

    Plesa, A.-C.; Knapmeyer, M.; Golombek, M. P.; Breuer, D.; Grott, M.; Kawamura, T.; Lognonné, P.; Tosi, N.; Weber, R. C.

    2018-03-01

    The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport mission, to be launched in 2018, will perform a comprehensive geophysical investigation of Mars in situ. The Seismic Experiment for Interior Structure package aims to detect global and regional seismic events and in turn offer constraints on core size, crustal thickness, and core, mantle, and crustal composition. In this study, we estimate the present-day amount and distribution of seismicity using 3-D numerical thermal evolution models of Mars, taking into account contributions from convective stresses as well as from stresses associated with cooling and planetary contraction. Defining the seismogenic lithosphere by an isotherm and assuming two end-member cases of 573 K and the 1073 K, we determine the seismogenic lithosphere thickness. Assuming a seismic efficiency between 0.025 and 1, this thickness is used to estimate the total annual seismic moment budget, and our models show values between 5.7 × 1016 and 3.9 × 1019 Nm.

  6. Seismic yield verification and a regional M/sub s/ vs m/sub b/ anomaly

    International Nuclear Information System (INIS)

    Rodean, H.C.

    1976-01-01

    The surface-wave magnitude (M/sub s/) and body-wave magnitude (m/sub b/) data for explosions in the western United States are anomalous with respect to such data for the Aleutians, the Sahara, and the USSR. The degree of this anomaly is such that it has significant implications with respect to using magnitude vs yield data from the Nevada Test Site to estimate the yields of explosions in other parts of the world. This report presents the results of a literature survey of seismic and other geophysical evidence relating to this anomaly. The geology and geophysics of three regions are considered: (1) the Basin and Range province in the western United States, (2) the Baikal rift zone in the USSR, and (3) central Kazakhstan in the USSR. Complete geophysical models, which would be of value in explaining the M/sub s/ vs m/sub b/ anomaly, have not been developed for any of these regions

  7. Seismic ground motion modelling and damage earthquake scenarios: A bridge between seismologists and seismic engineers

    International Nuclear Information System (INIS)

    Panza, G.F.; Romanelli, F.; Vaccari. F.; . E-mails: Luis.Decanini@uniroma1.it; Fabrizio.Mollaioli@uniroma1.it)

    2002-07-01

    The input for the seismic risk analysis can be expressed with a description of 'roundshaking scenarios', or with probabilistic maps of perhaps relevant parameters. The probabilistic approach, unavoidably based upon rough assumptions and models (e.g. recurrence and attenuation laws), can be misleading, as it cannot take into account, with satisfactory accuracy, some of the most important aspects like rupture process, directivity and site effects. This is evidenced by the comparison of recent recordings with the values predicted by the probabilistic methods. We prefer a scenario-based, deterministic approach in view of the limited seismological data, of the local irregularity of the occurrence of strong earthquakes, and of the multiscale seismicity model, that is capable to reconcile two apparently conflicting ideas: the Characteristic Earthquake concept and the Self Organized Criticality paradigm. Where the numerical modeling is successfully compared with records, the synthetic seismograms permit the microzoning, based upon a set of possible scenario earthquakes. Where no recordings are available the synthetic signals can be used to estimate the ground motion without having to wait for a strong earthquake to occur (pre-disaster microzonation). In both cases the use of modeling is necessary since the so-called local site effects can be strongly dependent upon the properties of the seismic source and can be properly defined only by means of envelopes. The joint use of reliable synthetic signals and observations permits the computation of advanced hazard indicators (e.g. damaging potential) that take into account local soil properties. The envelope of synthetic elastic energy spectra reproduces the distribution of the energy demand in the most relevant frequency range for seismic engineering. The synthetic accelerograms can be fruitfully used for design and strengthening of structures, also when innovative techniques, like seismic isolation, are employed. For these

  8. A synthetic seismicity model for the Middle America Trench

    Science.gov (United States)

    Ward, Steven N.

    1991-01-01

    A novel iterative technique, based on the concept of fault segmentation and computed using 2D static dislocation theory, for building models of seismicity and fault interaction which are physically acceptable and geometrically and kinematically correct, is presented. The technique is applied in two steps to seismicity observed at the Middle America Trench. The first constructs generic models which randomly draw segment strengths and lengths from a 2D probability distribution. The second constructs predictive models in which segment lengths and strengths are adjusted to mimic the actual geography and timing of large historical earthquakes. Both types of models reproduce the statistics of seismicity over five units of magnitude and duplicate other aspects including foreshock and aftershock sequences, migration of foci, and the capacity to produce both characteristic and noncharacteristic earthquakes. Over a period of about 150 yr the complex interaction of fault segments and the nonlinear failure conditions conspire to transform an apparently deterministic model into a chaotic one.

  9. Global regionalized seismicity in view of Non-Extensive Statistical Physics

    Science.gov (United States)

    Chochlaki, Kalliopi; Vallianatos, Filippos; Michas, Georgios

    2018-03-01

    In the present work we study the distribution of Earth's shallow seismicity on different seismic zones, as occurred from 1981 to 2011 and extracted from the Centroid Moment Tensor (CMT) catalog. Our analysis is based on the subdivision of the Earth's surface into seismic zones that are homogeneous with regards to seismic activity and orientation of the predominant stress field. For this, we use the Flinn-Engdahl regionalization (FE) (Flinn and Engdahl, 1965), which consists of fifty seismic zones as modified by Lombardi and Marzocchi (2007). The latter authors grouped the 50 FE zones into larger tectonically homogeneous ones, utilizing the cumulative moment tensor method, resulting into thirty-nine seismic zones. In each one of these seismic zones we study the distribution of seismicity in terms of the frequency-magnitude distribution and the inter-event time distribution between successive earthquakes, a task that is essential for hazard assessments and to better understand the global and regional geodynamics. In our analysis we use non-extensive statistical physics (NESP), which seems to be one of the most adequate and promising methodological tools for analyzing complex systems, such as the Earth's seismicity, introducing the q-exponential formulation as the expression of probability distribution function that maximizes the Sq entropy as defined by Tsallis, (1988). The qE parameter is significantly greater than one for all the seismic regions analyzed with value range from 1.294 to 1.504, indicating that magnitude correlations are particularly strong. Furthermore, the qT parameter shows some temporal correlations but variations with cut-off magnitude show greater temporal correlations when the smaller magnitude earthquakes are included. The qT for earthquakes with magnitude greater than 5 takes values from 1.043 to 1.353 and as we increase the cut-off magnitude to 5.5 and 6 the qT value ranges from 1.001 to 1.242 and from 1.001 to 1.181 respectively, presenting

  10. Evidence for a continental unstable triple junction as an alternate model for Vrancea seismicity

    International Nuclear Information System (INIS)

    Besutiu, L.

    2002-01-01

    The Vrancea active seismic zone located in the bending area of Romanian Carpathians stands for a long time as a challenge to geoscientists all over the world. Deep seismicity in continental collision circumstances is rather rare and always constraints on dynamics of subduction. The pattern of the intermediate-depth seismicity in the Vrancea region suggests a confined prismatic nearly vertical seismic body. The small size and geometry of the seismic zone have made it difficult to interpret the kinematics of subduction and continental collision in the area. During the years, several models, almost all subduction-related, have more or less successfully tried to explain this phenomenon. The paper represents an attempt to explain the Vrancea intermediate depth seismicity starting from a new concept, as introduced by the plate tectonics theory: the triple junction. A continental unstable triple junction is proposed as an alternate model to explain the unusual seismicity in the Vrancea seismic area. Three tectonic plates / microplates seem to join in the region: East European Plate (EEP), Moesian microplate (MoP), and the Intra-Alpine microplate (IaP). Their edges are geophysically documented and their motion is evidenced. The differentiation in their relative velocities generated an unstable transform-transform-compression triple junction that determined the vertical collapse of the lithospheric segment to which the intermediate seismicity within Vrancea zone is associated. Three major plates' wedges bound the seismic body: Tornquist-Teissyere zone, Peceneaga-Camena fault, and Trans-Getica fault. Temperature accommodation phenomena associated to the sinking lithospheric body into the hotter upper mantle environment (such as convective cells, phase-transform processes, and devolatilization) could be responsible for the earthquakes occurrence. The problem of the missing subduction related volcanism within Vrancea triple junction (VTJ) area is definitely solved in the case

  11. Light Water Reactor Sustainability Program Advanced Seismic Soil Structure Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Bolisetti, Chandrakanth [Idaho National Lab. (INL), Idaho Falls, ID (United States); Coleman, Justin Leigh [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-06-01

    Risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. Specifically, seismic probabilistic risk assessments (SPRAs) are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in some instances the current SPRA approach has large uncertainties, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility). SPRA’s are performed by convolving the seismic hazard (this is the estimate of all likely damaging earthquakes at the site of interest) with the seismic fragility (the conditional probability of failure of a structure, system, or component given the occurrence of earthquake ground motion). In this calculation, there are three main pieces to seismic risk quantification, 1) seismic hazard and nuclear power plants (NPPs) response to the hazard, 2) fragility or capacity of structures, systems and components (SSC), and 3) systems analysis. Two areas where NLSSI effects may be important in SPRA calculations are, 1) when calculating in-structure response at the area of interest, and 2) calculation of seismic fragilities (current fragility calculations assume a lognormal distribution for probability of failure of components). Some important effects when using NLSSI in the SPRA calculation process include, 1) gapping and sliding, 2) inclined seismic waves coupled with gapping and sliding of foundations atop soil, 3) inclined seismic waves coupled with gapping and sliding of deeply embedded structures, 4) soil dilatancy, 5) soil liquefaction, 6) surface waves, 7) buoyancy, 8) concrete cracking and 9) seismic isolation The focus of the research task presented here-in is on implementation of NLSSI into the SPRA calculation process when calculating in-structure response at the area

  12. Seismological database for Banat seismic region (Romania) - Part 1: The parametric earthquake catalogue

    International Nuclear Information System (INIS)

    Oros, E.; Popa, M.; Moldovan, I. A.

    2008-01-01

    The most comprehensive seismological database for Banat seismic region (Romania) has been achieved. This paper refers to the essential characteristics of the first component of this database, namely the Parametric Earthquakes Catalogue for the Banat Seismic Region (PECBSR). PECBSR comprises 7783 crustal earthquakes (3 ≤ h ≤ 25 km) with 0.4 ≤ M i ≥ 5.6 (M i is M L , M D , M S , M W , Mm and/or mb from compiled sources) occurred in the Banat region and its surroundings between years 1443 and 2006. Different magnitude scales were converted into moment magnitude scale, Mw. The completeness of PECBSR strongly depends on the time. (authors)

  13. Regional passive seismic monitoring reveals dynamic glacier activity on Spitsbergen, Svalbard

    Directory of Open Access Journals (Sweden)

    Andreas Köhler

    2015-12-01

    Full Text Available Dynamic glacier activity is increasingly observed through passive seismic monitoring. We analysed near-regional-scale seismicity on the Arctic archipelago of Svalbard to identify seismic icequake signals and to study their spatial–temporal distribution within the 14-year period from 2000 until 2013. This is the first study that uses seismic data recorded on permanent broadband stations to detect and locate icequakes in different regions of Spitsbergen, the main island of the archipelago. A temporary local seismic network and direct observations of glacier calving and surging were used to identify icequake sources. We observed a high number of icequakes with clear spectral peaks between 1 and 8 Hz in different parts of Spitsbergen. Spatial clusters of icequakes could be associated with individual grounded tidewater glaciers and exhibited clear seasonal variability each year with more signals observed during the melt season. Locations at the termini of glaciers, and correlation with visual calving observations in situ at Kronebreen, a glacier in the Kongsfjorden region, show that these icequakes were caused dominantly by calving. Indirect evidence for glacier surging through increased calving seismicity was found in 2003 at Tunabreen, a glacier in central Spitsbergen. Another type of icequake was observed in the area of the Nathorstbreen glacier system. Seismic events occurred upstream of the glacier within a short time period between January and May 2009 during the initial phase of a major glacier surge. This study is the first step towards the generation and implementation of an operational seismic monitoring strategy for glacier dynamics in Svalbard.

  14. Full-waveform seismic tomography of the Vrancea, Romania, subduction region

    Science.gov (United States)

    Baron, Julie; Morelli, Andrea

    2017-12-01

    The Vrancea region is one of the few locations of deep seismicity in Europe. Seismic tomography has been able to map lithospheric downwelling, but has not been able yet to clearly discriminate between competing geodynamic interpretations of the geological and geophysical evidence available. We study the seismic structure of the Vrancea subduction zone, using adjoint-based, full-waveform tomography to map the 3D vP and vS structure in detail. We use the database that was built during the CALIXTO (Carpathian Arc Lithosphere X-Tomography) temporary experiment, restricted to the broadband sensors and local intermediate-depth events. We fit waveforms with a cross-correlation misfit criterion in separate time windows around the expected P and S arrivals, and perform 17 iterations of vP and vS model updates (altogether, requiring about 16 million CPU hours) before reaching stable convergence. Among other features, our resulting model shows a nearly vertical, high-velocity body, that overlaps with the distribution of seismicity in its northeastern part. In its southwestern part, a slab appears to dip less steeply to the NW, and is suggestive of ongoing - or recently concluded - subduction geodynamic processes. Joint inversion for vP and vS allow us to address the vP/vS ratio distribution, that marks high vP/vS in the crust beneath the Focsani sedimentary basin - possibly due to high fluid pressure - and a low vP/vS edge along the lower plane of the subducting lithosphere, that in other similar environment has been attributed to dehydration of serpentine in the slab. In spite of the restricted amount of data available, and limitations on the usable frequency pass-band, full-waveform inversion reveals its potential to improve the general quality of imaging with respect to other tomographic techniques - although at a sensible cost in terms of computing resources. Our study also shows that re-analysis of legacy data sets with up-to-date techniques may bring new, useful

  15. Seismic risk control of nuclear power plants using seismic protection systems in stable continental regions: The UK case

    Energy Technology Data Exchange (ETDEWEB)

    Medel-Vera, Carlos, E-mail: cbmedel@uc.cl; Ji, Tianjian, E-mail: tianjian.ji@manchester.ac.uk

    2016-10-15

    Highlights: • Strategies to reduce seismic risk for nuclear power stations in the UK are analysed. • Efficiency of devices to reduce risk: viscous-based higher than hysteretic-based. • Scenario-based incremental dynamic analysis is introduced for use in nuclear stations. • Surfaces of seismic unacceptable performance for nuclear stations are proposed. - Abstract: This article analyses three different strategies on the use of seismic protection systems (SPS) for nuclear power plants (NPPs) in the UK. Such strategies are based on the experience reported elsewhere of seismically protected nuclear reactor buildings in other stable continental regions. Analyses are conducted using an example of application based on a 1000 MW Pressurised Water Reactor building located in a representative UK nuclear site. The efficiency of the SPS is probabilistically assessed to achieve possible risk reduction for both rock and soil sites in comparison with conventionally constructed NPPs. Further analyses are conducted to study how the reduction of risk changes when all controlling scenarios of the site are included. This is done by introducing a scenario-based incremental dynamic analysis aimed at the generation of surfaces for unacceptable performance of NPPs as a function of earthquake magnitude (M{sub w}) and distance-to-site (R{sub epi}). General guidelines are proposed to potentially use SPS in future NPPs in the UK. Such recommendations can be used by the British nuclear industry in the future development of 12 new reactors to be built in the next two decades to generate 16 GWe of new nuclear capacity.

  16. Integrate urban‐scale seismic hazard analyses with the U.S. National Seismic Hazard Model

    Science.gov (United States)

    Moschetti, Morgan P.; Luco, Nicolas; Frankel, Arthur; Petersen, Mark D.; Aagaard, Brad T.; Baltay, Annemarie S.; Blanpied, Michael; Boyd, Oliver; Briggs, Richard; Gold, Ryan D.; Graves, Robert; Hartzell, Stephen; Rezaeian, Sanaz; Stephenson, William J.; Wald, David J.; Williams, Robert A.; Withers, Kyle

    2018-01-01

    For more than 20 yrs, damage patterns and instrumental recordings have highlighted the influence of the local 3D geologic structure on earthquake ground motions (e.g., M">M 6.7 Northridge, California, Gao et al., 1996; M">M 6.9 Kobe, Japan, Kawase, 1996; M">M 6.8 Nisqually, Washington, Frankel, Carver, and Williams, 2002). Although this and other local‐scale features are critical to improving seismic hazard forecasts, historically they have not been explicitly incorporated into the U.S. National Seismic Hazard Model (NSHM, national model and maps), primarily because the necessary basin maps and methodologies were not available at the national scale. Instead,...

  17. First approximations in avalanche model validations using seismic information

    Science.gov (United States)

    Roig Lafon, Pere; Suriñach, Emma; Bartelt, Perry; Pérez-Guillén, Cristina; Tapia, Mar; Sovilla, Betty

    2017-04-01

    Avalanche dynamics modelling is an essential tool for snow hazard management. Scenario based numerical modelling provides quantitative arguments for decision-making. The software tool RAMMS (WSL Institute for Snow and Avalanche Research SLF) is one such tool, often used by government authorities and geotechnical offices. As avalanche models improve, the quality of the numerical results will depend increasingly on user experience on the specification of input (e.g. release and entrainment volumes, secondary releases, snow temperature and quality). New model developments must continue to be validated using real phenomena data, for improving performance and reliability. The avalanches group form University of Barcelona (RISKNAT - UB), has studied the seismic signals generated from avalanches since 1994. Presently, the group manages the seismic installation at SLF's Vallée de la Sionne experimental site (VDLS). At VDLS the recorded seismic signals can be correlated to other avalanche measurement techniques, including both advanced remote sensing methods (radars, videogrammetry) and obstacle based sensors (pressure, capacitance, optical sender-reflector barriers). This comparison between different measurement techniques allows the group to address the question if seismic analysis can be used alone, on more additional avalanche tracks, to gain insight and validate numerical avalanche dynamics models in different terrain conditions. In this study, we aim to add the seismic data as an external record of the phenomena, able to validate RAMMS models. The seismic sensors are considerable easy and cheaper to install than other physical measuring tools, and are able to record data from the phenomena in every atmospheric conditions (e.g. bad weather, low light, freezing make photography, and other kind of sensors not usable). With seismic signals, we record the temporal evolution of the inner and denser parts of the avalanche. We are able to recognize the approximate position

  18. In-situ measurements of seismic velocities in the San Francisco Bay Region; part III

    Science.gov (United States)

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.; Roth, Edward F.

    1977-01-01

    Seismic wave velocities (compressional and shear) are important parameters for estimating the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. In the current program seismic velocities have been measured at 59 locations 1n the San Francisco Bay Region. This report is the third in a series of Open-File Reports and describes the in-situ velocity measurements at locations 35-59. At each location seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill cuttings, undisturbed (cored) samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the sites. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. There is a variety of geologic and seismic data available in the San Francisco Bay Region for use 1n developing the general zoning techniques which can then be applied to other areas. Shear wave velocities 1n near-surface geologic materials are of especial interest for engineering seismology and seismic zonation studies, yet in general, they are difficult to measure because of contamination by compressional waves. A comparison of various in-situ techniques by Warrick (1974) establishes the reliability of the method utilizing a "horizontal traction" source for sites underlain by bay mud and alluvium. Gibbs, and others (1975a) present data from 12 holes and establishes the reliability of the method for sites underlain by a variety of different rock units and suggest extending the measurements to

  19. Evolution and strengthening of the Calabrian Regional Seismic Network during the Pollino sequence

    Science.gov (United States)

    D'Alessandro, Antonino; Gervasi, Anna; Guerra, Ignazio

    2013-04-01

    In the last three years the Calabria-Lucania border area is affected by an intense seismic activity generated by the activation of geological structures which be seat of clusters of microearthquakes, with energy release sufficient to be felt and to generate alarm and bother. Besides to the historical memory of the inhabitants of Mormanno (the town most affected of macroseismic effects) there are some historical documents that indicate the occurrence of a similar seismic crisis in 1888. A more recent seismic sequence, the first monitored by seismic instruments, occurred in 1973-1974. In the last case, the activity started in early 2010 and is still ongoing. The two shocks of ML = 4.3 and 5.0 and the the very long time duration differs this crisis from the previous ones. Given this background, in 1981 was installed at Mormanno a seismic station (MMN) belonging to Regional Seismic Network of the University of Calabria (RSRC), now also a station of the Italian National Seismic Network of the Istituto Nazionale di Geofisica Vulcanolgia (INSN-INGV). This seismic station made it possible to follow the evolution of seismicity in this area and in particular the progressive increase in seismic activity started in 2010. Since 2010, some 3D stand-alone, was installed by the University of Calabria. Further stations of INGV were installed in November 2011 after a sharp increase of the energy release and subsequently by the INGV and the GeoForschungsZentrum (Potsdam) after the main shock of the whole sequence. Seismic networks are powerful tools for understanding active tectonic processes in a monitored seismically active region. However, the optimal monitoring of a seismic region requires the assessment of the seismic network capabilities to identify seismogenic areas that are not adequately covered and to quantify measures that will allow the network improvement. In this paper we examine in detail the evolution and the strengthening of the RSRC in the last years analyzing the

  20. Seismic anisotropy and its relation with crust structure and stress field in the Reggio Emilia Region (Northern Italy)

    Science.gov (United States)

    Margheriti, L.; Ferulano, M. F.; Di Bona, M.

    2006-11-01

    Shear wave splitting is measured at 14 seismic stations in the Reggio Emilia region above local background seismicity and two sequences of seismic events. The good quality of the waveforms together with the favourable distribution of earthquake foci allows us to place strong constraints on the geometry and the depth of the anisotropic volume. It is about 60 km2 wide and located between 6 and 11 km depth, inside Mesozoic age carbonate rocks. The splitting results suggest also the presence of a shallower anisotropic layer about 1 km thick and few km wide in the Pliocene-Quaternary alluvium above the Mesozoic layer. The fast polarization directions (N30°E) are approximately parallel to the maximum horizontal stress (σ1 is SSW-NNE) in the region and also parallel to the strike of the main structural features in the Reggio Emilia area. The size of the delay times suggests about 4.5 per cent shear wave velocity anisotropy. These parameters agree with an interpretation of seismic anisotropy in terms of the extensive-dilatancy anisotropy model which considers the rock volume to be pervaded by fluid-saturated microcracks aligned by the active stress field. We cannot completely rule out the contribution of aligned macroscopic fractures as the cause of the shear wave anisotropy even if the parallel shear wave polarizations we found are diagnostic of transverse isotropy with a horizontal axis of symmetry. This symmetry is commonly explained by parallel stress-aligned microcracks.

  1. Transient postseismic mantle relaxation following 2004 Sumatra earthquake: implications of seismic vulnerability in the Andaman-Nicobar region

    Directory of Open Access Journals (Sweden)

    C. D. Reddy

    2012-02-01

    Full Text Available Throughout the world, the tsunami generation potential of some large under-sea earthquakes significantly contributes to regional seismic hazard, which gives rise to significant risk in the near-shore provinces where human settlements are in sizeable population, often referred to as coastal seismic risk. In this context, we show from the pertinent GPS data that the transient stresses generated by the viscoelastic relaxation process taking place in the mantle is capable of rupturing major faults by stress transfer from the mantle through the lower crust including triggering additional rupture on the other major faults. We also infer that postseismic relaxation at relatively large depths can push some of the fault segments to reactivation causing failure sequences. As an illustration to these effects, we consider in detail the earthquake sequence comprising six events, starting from the main event of Mw = 7.5, on 10 August 2009 and tapering off to a small earthquake of Mw = 4.5 on 2 February 2011 over a period of eighteen months in the intensely seismic Andaman Islands between India and Myanmar. The persisting transient stresses, spatio-temporal seismic pattern, modeled Coulomb stress changes, and the southward migration of earthquake activity has increased the probability of moderate earthquakes recurring in the northern Andaman region, particularly closer to or somewhat south of Diglipur.

  2. A Bimodal Hybrid Model for Time-Dependent Probabilistic Seismic Hazard Analysis

    Science.gov (United States)

    Yaghmaei-Sabegh, Saman; Shoaeifar, Nasser; Shoaeifar, Parva

    2018-03-01

    The evaluation of evidence provided by geological studies and historical catalogs indicates that in some seismic regions and faults, multiple large earthquakes occur in cluster. Then, the occurrences of large earthquakes confront with quiescence and only the small-to-moderate earthquakes take place. Clustering of large earthquakes is the most distinguishable departure from the assumption of constant hazard of random occurrence of earthquakes in conventional seismic hazard analysis. In the present study, a time-dependent recurrence model is proposed to consider a series of large earthquakes that occurs in clusters. The model is flexible enough to better reflect the quasi-periodic behavior of large earthquakes with long-term clustering, which can be used in time-dependent probabilistic seismic hazard analysis with engineering purposes. In this model, the time-dependent hazard results are estimated by a hazard function which comprises three parts. A decreasing hazard of last large earthquake cluster and an increasing hazard of the next large earthquake cluster, along with a constant hazard of random occurrence of small-to-moderate earthquakes. In the final part of the paper, the time-dependent seismic hazard of the New Madrid Seismic Zone at different time intervals has been calculated for illustrative purpose.

  3. Seismic behaviour of PWR fuel assemblies model and its validation

    International Nuclear Information System (INIS)

    Queval, J.C.; Gantenbein, F.; Brochard, D.; Benjedidia, A.

    1991-01-01

    The validity of the models simulating the seismic behaviour of PWR cores can only be exactly demonstrated by seismic testing on groups of fuel assemblies. Shake table seismic tests of rows of assembly mock-ups, conducted by the CEA in conjunction with FRAMATOME, are presented in reference /1/. This paper addresses the initial comparisons between model and test results for a row of five assemblies in air. Two models are used: a model with a single beam per assembly, used regularly in accident analyses, and described in reference /2/, and a more refined 2-beam per assembly model, geared mainly towards interpretation of test results. The 2-beam model is discussed first, together with parametric studies used to characterize it, and the study of the assembly row for a period limited to 2 seconds and for different excitation levels. For the 1-beam model assembly used in applications, the row is studied over the total test time, i.e twenty seconds, which covers the average duration of the core seismic behaviour studies, and for a peak exciting acceleration value at 0.4 g, which corresponds to the SSE level of the reference spectrum

  4. Scale modeling of reinforced concrete structures subjected to seismic loading

    International Nuclear Information System (INIS)

    Dove, R.C.

    1983-01-01

    Reinforced concrete, Category I structures are so large that the possibility of seismicly testing the prototype structures under controlled conditions is essentially nonexistent. However, experimental data, from which important structural properties can be determined and existing and new methods of seismic analysis benchmarked, are badly needed. As a result, seismic experiments on scaled models are of considerable interest. In this paper, the scaling laws are developed in some detail so that assumptions and choices based on judgement can be clearly recognized and their effects discussed. The scaling laws developed are then used to design a reinforced concrete model of a Category I structure. Finally, how scaling is effected by various types of damping (viscous, structural, and Coulomb) is discussed

  5. Study of attenuation structure for central Anatolia region, Turkey based on Keskin seismic array data

    Science.gov (United States)

    Semin, K. U.; Ozel, N. M.

    2011-12-01

    Central Anatolia is bounded in the north by the well-known north Anatolian fault system (NAFS) and on the south-southwest is bounded by the east Anatolian fault system (EAFS). The central area does not have major faults and acts as a single block moving westward. This region is not considered as seismically active as the NAFS or EAFS but the recent moderate-size Bala earthquakes (Ml=5.7, Ml= 5.5) on 20 and 27 December 2007 near the Tuz golu fault may be an indication of future seismic activity. In order to get a better picture of the crustal structure of this region we applied Coda Normalization method for the measurement of Qs-1 as a function of frequency for the frequencies 1.5, 3, 6, 8 Hz. 20 and 27 December 2007 Bala earthquakes (Ml magnitude 5.6 an 5.5) and their aftershocks recorded by the Keskin seismic array (International Monitoring System code BRTR) is analyzed in this study. Keskin seismic array has a small aperture circular design with 6 vertical short period and 1 broadband borehole seismometers. In addition, Multiple Lapse Time Window Analysis (MLTWA) method was applied to the data for the separation of intrinsic and scattering attenuation inm the region at the same frequencies. MLTWA method allowed a separation between the intrinsic attenuation and scattering attenuation. Preliminary results show a relatively low attenuation compared to western and eastern anatolia regions. This might be explained by the less seismicity in the region. A study of the regional and site attenuation of seismic waves of earthquakes in this area will contribute in predicting earthquake generated ground-motion and becomes vital in making decisions for earthquake regulations, building codes and to monitoring nuclear explosions.

  6. Summary report of seismic PSA of BWR model plant

    International Nuclear Information System (INIS)

    1999-05-01

    This report presents a seismic PSA (Probabilistic Safety Assessment) methodology developed at the Japan Atomic Energy Research Institute (JAERI) for evaluating risks of nuclear power plants (NPPs) and the results from an application of the methodology to a BWR plant in Japan, which is termed Model Plant'. The seismic PSA procedures developed at JAERI are to evaluate core damage frequency (CDF) and have the following four steps: (1) evaluation of seismic hazard, (2) evaluation of realistic response, (3) evaluation of component capacities and failure probabilities, and (4) evaluation of conditional probability of system failure and CDF. Although these procedures are based on the methodologies established and used in the United States, they include several unique features: (1) seismic hazard analysis is performed with use of available knowledge and database on seismological conditions in Japan; (2) response evaluation is performed with a response factor method which is cost effective and associated uncertainties can be reduced with use of modern methods of design calculations; (3) capacity evaluation is performed with use of test results available in Japan in combination with design information and generic capacity data in the U.S.A.; (4) systems reliability analysis, performed with use of the computer code SECOM-2 developed at JAERI, includes identification of dominant accident sequences, importance analysis of components and systems as well as the CDF evaluation with consideration of the effect of correlation of failures by a newly developed method based on the Monte Carlo method. The effect of correlation has been recognized as an important issue in seismic PSAs. The procedures was used to perform a seismic PSA of a 1100 MWe BWR plant. Results are shown as well as the insights derived and future research needs identified in this seismic PSA. (J.P.N.)

  7. A Geo-referenced 3D model of the Juan de Fuca Slab and associated seismicity

    Science.gov (United States)

    Blair, J.L.; McCrory, P.A.; Oppenheimer, D.H.; Waldhauser, F.

    2011-01-01

    We present a Geographic Information System (GIS) of a new 3-dimensional (3D) model of the subducted Juan de Fuca Plate beneath western North America and associated seismicity of the Cascadia subduction system. The geo-referenced 3D model was constructed from weighted control points that integrate depth information from hypocenter locations and regional seismic velocity studies. We used the 3D model to differentiate earthquakes that occur above the Juan de Fuca Plate surface from earthquakes that occur below the plate surface. This GIS project of the Cascadia subduction system supersedes the one previously published by McCrory and others (2006). Our new slab model updates the model with new constraints. The most significant updates to the model include: (1) weighted control points to incorporate spatial uncertainty, (2) an additional gridded slab surface based on the Generic Mapping Tools (GMT) Surface program which constructs surfaces based on splines in tension (see expanded description below), (3) double-differenced hypocenter locations in northern California to better constrain slab location there, and (4) revised slab shape based on new hypocenter profiles that incorporate routine depth uncertainties as well as data from new seismic-reflection and seismic-refraction studies. We also provide a 3D fly-through animation of the model for use as a visualization tool.

  8. Distribution of ground rigidity and ground model for seismic response analysis in Hualian project of large scale seismic test

    International Nuclear Information System (INIS)

    Kokusho, T.; Nishi, K.; Okamoto, T.; Tanaka, Y.; Ueshima, T.; Kudo, K.; Kataoka, T.; Ikemi, M.; Kawai, T.; Sawada, Y.; Suzuki, K.; Yajima, K.; Higashi, S.

    1997-01-01

    An international joint research program called HLSST is proceeding. HLSST is large-scale seismic test (LSST) to investigate soil-structure interaction (SSI) during large earthquake in the field in Hualien, a high seismic region in Taiwan. A 1/4-scale model building was constructed on the gravelly soil in this site, and the backfill material of crushed stone was placed around the model plant after excavation for the construction. Also the model building and the foundation ground were extensively instrumental to monitor structure and ground response. To accurately evaluate SSI during earthquakes, geotechnical investigation and forced vibration test were performed during construction process namely before/after base excavation, after structure construction and after backfilling. And the distribution of the mechanical properties of the gravelly soil and the backfill are measured after the completion of the construction by penetration test and PS-logging etc. This paper describes the distribution and the change of the shear wave velocity (V s ) measured by the field test. Discussion is made on the effect of overburden pressure during the construction process on V s in the neighbouring soil and, further on the numerical soil model for SSI analysis. (orig.)

  9. Numerical modeling of landslides and generated seismic waves: The Bingham Canyon Mine landslides

    Science.gov (United States)

    Miallot, H.; Mangeney, A.; Capdeville, Y.; Hibert, C.

    2016-12-01

    Landslides are important natural hazards and key erosion processes. They create long period surface waves that can be recorded by regional and global seismic networks. The seismic signals are generated by acceleration/deceleration of the mass sliding over the topography. They consist in a unique and powerful tool to detect, characterize and quantify the landslide dynamics. We investigate here the processes at work during the two massive landslides that struck the Bingham Canyon Mine on the 10th April 2013. We carry a combined analysis of the generated seismic signals and the landslide processes computed with a 3D modeling on a complex topography. Forces computed by broadband seismic waveform inversion are used to constrain the study and particularly the force-source and the bulk dynamic. The source time function are obtained by a 3D model (Shaltop) where rheological parameters can be adjusted. We first investigate the influence of the initial shape of the sliding mass which strongly affects the whole landslide dynamic. We also see that the initial shape of the source mass of the first landslide constrains pretty well the second landslide source mass. We then investigate the effect of a rheological parameter, the frictional angle, that strongly influences the resulted computed seismic source function. We test here numerous friction laws as the frictional Coulomb law and a velocity-weakening friction law. Our results show that the force waveform fitting the observed data is highly variable depending on these different choices.

  10. Thermal regime of the lithosphere and prediction of seismic hazard in the Caspian region

    International Nuclear Information System (INIS)

    Levin, L.E.; Solodilov, L.N.; Kondorskaya, N.V.; Gasanov, A.G; Panahi, B.M.

    2002-01-01

    Full text : Prediction of seicmicity is one of elements of ecology hazard warning. In this collective research, it is elaborated in three directions : quantitative estimate of regional faults by level of seismic activity; ascertainment of space position of earthquake risk zones, determination of high seismic potential sites for the period of the next 3-5 years. During elaboration of prediction, it takes into account that peculiar feature all over the is determined by relationship of about 90 percent of earthquake hypocenters and released energy of seismic waves with elactic-brittle ayer of the lithosphere. Concetration of earthquakes epicenters is established predominantly in zones of complex structure of elastic-brittle layer where gradient of it thickness is 20-30 km. Directions of hypocenters migration in the plastic-viscous layer reveal a space position of seismic dangerous zones. All this provides a necessity for generalization of data on location of earthquakes epicenters; determination of their magnitudes, space position of regional faults and heat flow with calculation of thermal regime being made for clarification of the lithosphere and elastic-brittle thickness variations separately. General analysis includes a calculation of released seismic wave energy and determination of peculiar features of its distribution in the entire region and also studies of hypocenters migration in the plastic-viscous layer of the litosphere in time.

  11. Seismic waves and earthquakes in a global monolithic model

    Science.gov (United States)

    Roubíček, Tomáš

    2018-03-01

    The philosophy that a single "monolithic" model can "asymptotically" replace and couple in a simple elegant way several specialized models relevant on various Earth layers is presented and, in special situations, also rigorously justified. In particular, global seismicity and tectonics is coupled to capture, e.g., (here by a simplified model) ruptures of lithospheric faults generating seismic waves which then propagate through the solid-like mantle and inner core both as shear (S) or pressure (P) waves, while S-waves are suppressed in the fluidic outer core and also in the oceans. The "monolithic-type" models have the capacity to describe all the mentioned features globally in a unified way together with corresponding interfacial conditions implicitly involved, only when scaling its parameters appropriately in different Earth's layers. Coupling of seismic waves with seismic sources due to tectonic events is thus an automatic side effect. The global ansatz is here based, rather for an illustration, only on a relatively simple Jeffreys' viscoelastic damageable material at small strains whose various scaling (limits) can lead to Boger's viscoelastic fluid or even to purely elastic (inviscid) fluid. Self-induced gravity field, Coriolis, centrifugal, and tidal forces are counted in our global model, as well. The rigorous mathematical analysis as far as the existence of solutions, convergence of the mentioned scalings, and energy conservation is briefly presented.

  12. Numerical modeling of the 2017 active seismic infrasound balloon experiment

    Science.gov (United States)

    Brissaud, Q.; Komjathy, A.; Garcia, R.; Cutts, J. A.; Pauken, M.; Krishnamoorthy, S.; Mimoun, D.; Jackson, J. M.; Lai, V. H.; Kedar, S.; Levillain, E.

    2017-12-01

    We have developed a numerical tool to propagate acoustic and gravity waves in a coupled solid-fluid medium with topography. It is a hybrid method between a continuous Galerkin and a discontinuous Galerkin method that accounts for non-linear atmospheric waves, visco-elastic waves and topography. We apply this method to a recent experiment that took place in the Nevada desert to study acoustic waves from seismic events. This experiment, developed by JPL and its partners, wants to demonstrate the viability of a new approach to probe seismic-induced acoustic waves from a balloon platform. To the best of our knowledge, this could be the only way, for planetary missions, to perform tomography when one faces challenging surface conditions, with high pressure and temperature (e.g. Venus), and thus when it is impossible to use conventional electronics routinely employed on Earth. To fully demonstrate the effectiveness of such a technique one should also be able to reconstruct the observed signals from numerical modeling. To model the seismic hammer experiment and the subsequent acoustic wave propagation, we rely on a subsurface seismic model constructed from the seismometers measurements during the 2017 Nevada experiment and an atmospheric model built from meteorological data. The source is considered as a Gaussian point source located at the surface. Comparison between the numerical modeling and the experimental data could help future mission designs and provide great insights into the planet's interior structure.

  13. Modeling the Excitation of Seismic Waves by the Joplin Tornado

    Science.gov (United States)

    Valovcin, Anne; Tanimoto, Toshiro

    2017-10-01

    Tornadoes generate seismic signals when they contact the ground. Here we examine the signals excited by the Joplin tornado, which passed within 2 km of a station in the Earthscope Transportable Array. We model the tornado-generated vertical seismic signal at low frequencies (0.01-0.03 Hz) and solve for the strength of the seismic source. The resulting source amplitude is largest when the tornado was reported to be strongest (EF 4-5), and the amplitude is smallest when the tornado was weak (EF 0-2). A further understanding of the relationship between source amplitude and tornado intensity could open up new ways to study tornadoes from the ground.

  14. Modeling of seismic data in the downward continuation approach

    NARCIS (Netherlands)

    Stolk, C.C.; de Hoop, Maarten V.

    2005-01-01

    Seismic data are commonly modeled by a high-frequency single scattering approximation. This amounts to a linearization in the medium coefficient about a smooth background. The discontinuities are contained in the medium perturbation. The high-frequency part of the wavefield in the background medium

  15. Models for seismic wave propagation in periodically layered porous media

    NARCIS (Netherlands)

    Kudarova, A.; Van Dalen, K.N.; Drijkoningen, G.G.

    2014-01-01

    Several models are discussed for seismic wave propagation in periodically layered poroelastic media where layers represent mesoscopic-scale heterogeneities that are larger than the pore and grain sizes but smaller than the wavelength. The layers behave according to Biot’s theory. Wave propagation

  16. Added-value joint source modelling of seismic and geodetic data

    Science.gov (United States)

    Sudhaus, Henriette; Heimann, Sebastian; Walter, Thomas R.; Krueger, Frank

    2013-04-01

    In tectonically active regions earthquake source studies strongly support the analysis of the current faulting processes as they reveal the location and geometry of active faults, the average slip released or more. For source modelling of shallow, moderate to large earthquakes often a combination of geodetic (GPS, InSAR) and seismic data is used. A truly joint use of these data, however, usually takes place only on a higher modelling level, where some of the first-order characteristics (time, centroid location, fault orientation, moment) have been fixed already. These required basis model parameters have to be given, assumed or inferred in a previous, separate and highly non-linear modelling step using one of the these data sets alone. We present a new earthquake rupture model implementation that realizes a fully combined data integration of surface displacement measurements and seismic data in a non-linear optimization of simple but extended planar ruptures. The model implementation allows for fast forward calculations of full seismograms and surface deformation and therefore enables us to use Monte Carlo global search algorithms. Furthermore, we benefit from the complementary character of seismic and geodetic data, e. g. the high definition of the source location from geodetic data and the sensitivity of the resolution of the seismic data on moment releases at larger depth. These increased constraints from the combined dataset make optimizations efficient, even for larger model parameter spaces and with a very limited amount of a priori assumption on the source. A vital part of our approach is rigorous data weighting based on the empirically estimated data errors. We construct full data error variance-covariance matrices for geodetic data to account for correlated data noise and also weight the seismic data based on their signal-to-noise ratio. The estimation of the data errors and the fast forward modelling opens the door for Bayesian inferences of the source

  17. Dissonance and harmony between global and regional-scale seismic anisotropy and mantle dynamics

    Science.gov (United States)

    Becker, T. W.

    2017-12-01

    Huge numbers of SKS splitting observations and improved surface-wave based models of azimuthal anisotropy have advanced our understanding of how convection is recorded in mantle fabrics in the upper mantle. However, we are still debating the relative importance of frozen to actively forming olivine fabrics, subduction zone anisotropy lacks a clear reference model, and regional marine studies yield conflicting evidence as to what exactly is going on at the base of the plates and below. Here, I review the degree of agreement between regional and global observations of seismic anisotropy and how well those may be matched by first-order mantle convection models. Updated bean counting can help contextualize the spatial scales of alignment, and I discuss several examples of the relative roles of plate shear to mantle density anomalies and frozen-in structure for oceanic and continental plates. Resolution of seismological models is globally uneven, but there are some locales where such exercises may yield information on the relative strength of asthenosphere and mantle. Another long-standing question is how olivine fabrics record flow under different stress and volatile conditions. I illustrate how different petrological assumptions might be used to reconcile observations of azimuthal dependency of wave speeds for both Love and Rayleigh waves, and how this could improve our models of the upper mantle, much in the spirit of Montagner's vectorial tomography. This is but one approach to improve the regional realism of global geodynamic background models to understand where in space and time dissonance arises, and if a harmonious model may yet be constructed given our assumptions about the workings of the mantle.

  18. Study on relationship between evolution of regional gravity field and seismic hazard

    Science.gov (United States)

    Li, W.; Xu, C.; Shen, C.

    2017-12-01

    The lack of anomalous signal is a big issue for the study of geophysics using historical geodesy observations, which is a relatively new area of earth gravimetry application in seismology. Hence the use of the gravity anomaly (GA) derived from either a global geopotential model (GGM) or a regional gravity reanalysis (Ground Gravity Survey, GGS) becomes an important alternative solution. In this study, the GGS at 186 points for the period of 2010 2014 in the Sichuan-Yunnan region (SYR) stations are analyzed. To study the temporal and spatial distribution characteristics of regional gravity filed (RGF) and its evolution mechanism. Taking the geological and geophysical data as constraints. From the GGM expanded up to degree 360, GA were obtained after gravity reduction, especially removing the reference field. The dynamically evolutional characteristics of gravity field are closely relative to fault activity. The gravity changes with time about 5 years at LongMenShan fault (LMSF) have a slop of -12.83±2.9 μGal/a, indicating that LMSF has an uplift. To test the signal extraction algorithm in some geodynamic processes, GA from the SYR were inverted and it was also imposed as a priori information. Fortunately, some significant gravity variation have been detected at some stations in the thrust fault before and after four earthquakes, in which typical anomalies (earthquake precursor, EP) were positive GA variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the Lushan earthquake (Ms 7.0). The repeated observation results during about 5 years indicate that no significant gravity changes related to other geodynamical events were observed in most observation epochs. In addition, the mechanism of gravity changes at Lushan was also explored. We calculated the gravity change rates based on the model of Songpan-Ganze block (SGB) to Sichuan basin (SCB). And the changes is in good agreement with observed one, indicating

  19. Fault specific GIS based seismic hazard maps for the Attica region, Greece

    Science.gov (United States)

    Deligiannakis, G.; Papanikolaou, I. D.; Roberts, G.

    2018-04-01

    Traditional seismic hazard assessment methods are based on the historical seismic records for the calculation of an annual probability of exceedance for a particular ground motion level. A new fault-specific seismic hazard assessment method is presented, in order to address problems related to the incompleteness and the inhomogeneity of the historical records and to obtain higher spatial resolution of hazard. This method is applied to the region of Attica, which is the most densely populated area in Greece, as nearly half of the country's population lives in Athens and its surrounding suburbs, in the Greater Athens area. The methodology is based on a database of 24 active faults that could cause damage to Attica in case of seismic rupture. This database provides information about the faults slip rates, lengths and expected magnitudes. The final output of the method is four fault-specific seismic hazard maps, showing the recurrence of expected intensities for each locality. These maps offer a high spatial resolution, as they consider the surface geology. Despite the fact that almost half of the Attica region lies on the lowest seismic risk zone according to the official seismic hazard zonation of Greece, different localities have repeatedly experienced strong ground motions during the last 15 kyrs. Moreover, the maximum recurrence for each intensity occurs in different localities across Attica. Highest recurrence for intensity VII (151-156 times over 15 kyrs, or up to a 96 year return period) is observed in the central part of the Athens basin. The maximum intensity VIII recurrence (115 times over 15 kyrs, or up to a 130 year return period) is observed in the western part of Attica, while the maximum intensity IX (73-77/15 kyrs, or a 195 year return period) and X (25-29/15 kyrs, or a 517 year return period) recurrences are observed near the South Alkyonides fault system, which dominates the strong ground motions hazard in the western part of the Attica mainland.

  20. Building an Ensemble Seismic Hazard Model for the Magnitude Distribution by Using Alternative Bayesian Implementations

    Science.gov (United States)

    Taroni, M.; Selva, J.

    2017-12-01

    In this work we show how we built an ensemble seismic hazard model for the magnitude distribution for the TSUMAPS-NEAM EU project (http://www.tsumaps-neam.eu/). The considered source area includes the whole NEAM region (North East Atlantic, Mediterranean and connected seas). We build our models by using the catalogs (EMEC and ISC), their completeness and the regionalization provided by the project. We developed four alternative implementations of a Bayesian model, considering tapered or truncated Gutenberg-Richter distributions, and fixed or variable b-value. The frequency size distribution is based on the Weichert formulation. This allows for simultaneously assessing all the frequency-size distribution parameters (a-value, b-value, and corner magnitude), using multiple completeness periods for the different magnitudes. With respect to previous studies, we introduce the tapered Pareto distribution (in addition to the classical truncated Pareto), and we build a novel approach to quantify the prior distribution. For each alternative implementation, we set the prior distributions using the global seismic data grouped according to the different types of tectonic setting, and assigned them to the related regions. The estimation is based on the complete (not declustered) local catalog in each region. Using the complete catalog also allows us to consider foreshocks and aftershocks in the seismic rate computation: the Poissonicity of the tsunami events (and similarly the exceedances of the PGA) will be insured by the Le Cam's theorem. This Bayesian approach provides robust estimations also in the zones where few events are available, but also leaves us the possibility to explore the uncertainty associated with the estimation of the magnitude distribution parameters (e.g. with the classical Metropolis-Hastings Monte Carlo method). Finally we merge all the models with their uncertainty to create the ensemble model that represents our knowledge of the seismicity in the

  1. Toe-of-slope of a Cretaceous carbonate platform in outcrop, seismic model and offshore seismic data (Apulia, Italy)

    Science.gov (United States)

    Bracco Gartner, Guido; Morsilli, Michele; Schlager, Wolfgang; Bosellini, Alfonso

    Synthetic seismic models of outcrops in the Early Cretaceous slope of a carbonate platform on the Gargano Promontory (southern Italy) were compared to an offshore seismic section south of the Promontory. Outcrops of the same age on the promontory have the same sequence stratigraphic characteristics as their offshore equivalent, and are the only areas where the transition from platform to basin of Early Cretaceous is exposed on land. Two adjacent outcrop areas were combined into one seismic-scale lithologic model with the aid of photo mosaics, measured sections, and biostratigraphic data. Velocity, density, and porosity measurements on spot samples were used to construct the impedance model. Seismic models were generated by vertical incidence and finite difference programs. The results indicate that the reflections in the seismic model are controlled by the impedance contrast between low porous intervals rich in debris from the platform and highly porous intervals of pelagic lime mudstone, nearly devoid of debris. Finite difference seismic display showed best resemblance with the real seismic data, especially by mapping a drowning unconformity.

  2. Radiated Seismic Energy of Earthquakes in the South-Central Region of the Gulf of California, Mexico

    Science.gov (United States)

    Castro, Raúl R.; Mendoza-Camberos, Antonio; Pérez-Vertti, Arturo

    2018-05-01

    We estimated the radiated seismic energy (ES) of 65 earthquakes located in the south-central region of the Gulf of California. Most of these events occurred along active transform faults that define the Pacific-North America plate boundary and have magnitudes between M3.3 and M5.9. We corrected the spectral records for attenuation using nonparametric S-wave attenuation functions determined with the whole data set. The path effects were isolated from the seismic source using a spectral inversion. We computed radiated seismic energy of the earthquakes by integrating the square velocity source spectrum and estimated their apparent stresses. We found that most events have apparent stress between 3 × 10-4 and 3 MPa. Model independent estimates of the ratio between seismic energy and moment (ES/M0) indicates that this ratio is independent of earthquake size. We conclude that in general the apparent stress is low (σa < 3 MPa) in the south-central and southern Gulf of California.

  3. Seismic Hazard and risk assessment for Romania -Bulgaria cross-border region

    Science.gov (United States)

    Simeonova, Stela; Solakov, Dimcho; Alexandrova, Irena; Vaseva, Elena; Trifonova, Petya; Raykova, Plamena

    2016-04-01

    Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic hazard and vulnerability to earthquakes are steadily increasing as urbanization and development occupy more areas that are prone to effects of strong earthquakes. The assessment of the seismic hazard and risk is particularly important, because it provides valuable information for seismic safety and disaster mitigation, and it supports decision making for the benefit of society. Romania and Bulgaria, situated in the Balkan Region as a part of the Alpine-Himalayan seismic belt, are characterized by high seismicity, and are exposed to a high seismic risk. Over the centuries, both countries have experienced strong earthquakes. The cross-border region encompassing the northern Bulgaria and southern Romania is a territory prone to effects of strong earthquakes. The area is significantly affected by earthquakes occurred in both countries, on the one hand the events generated by the Vrancea intermediate-depth seismic source in Romania, and on the other hand by the crustal seismicity originated in the seismic sources: Shabla (SHB), Dulovo, Gorna Orjahovitza (GO) in Bulgaria. The Vrancea seismogenic zone of Romania is a very peculiar seismic source, often described as unique in the world, and it represents a major concern for most of the northern part of Bulgaria as well. In the present study the seismic hazard for Romania-Bulgaria cross-border region on the basis of integrated basic geo-datasets is assessed. The hazard results are obtained by applying two alternative approaches - probabilistic and deterministic. The MSK64 intensity (MSK64 scale is practically equal to the new EMS98) is used as output parameter for the hazard maps. We prefer to use here the macroseismic intensity instead of PGA, because it is directly related to the degree of damages and, moreover, the epicentral intensity is the original

  4. Post-seismic relaxation theory on laterally heterogeneous viscoelastic model

    Science.gov (United States)

    Pollitz, F.F.

    2003-01-01

    Investigation was carried out into the problem of relaxation of a laterally heterogeneous viscoelastic Earth following an impulsive moment release event. The formal solution utilizes a semi-analytic solution for post-seismic deformation on a laterally homogeneous Earth constructed from viscoelastic normal modes, followed by application of mode coupling theory to derive the response on the aspherical Earth. The solution is constructed in the Laplace transform domain using the correspondence principle and is valid for any linear constitutive relationship between stress and strain. The specific implementation described in this paper is a semi-analytic discretization method which assumes isotropic elastic structure and a Maxwell constitutive relation. It accounts for viscoelastic-gravitational coupling under lateral variations in elastic parameters and viscosity. For a given viscoelastic structure and minimum wavelength scale, the computational effort involved with the numerical algorithm is proportional to the volume of the laterally heterogeneous region. Examples are presented of the calculation of post-seismic relaxation with a shallow, laterally heterogeneous volume following synthetic impulsive seismic events, and they illustrate the potentially large effect of regional 3-D heterogeneities on regional deformation patterns.

  5. Passive seismic experiment in the Olduvai Gorge and Laetoli region (Ngorongoro Conservation Area), Northern Tanzania.

    Science.gov (United States)

    Parisi, Laura; Lombardo, Luigi; Tang, Zheng; Mai, P. Martin

    2017-04-01

    The Olduvai Gorge and Laetoli basins, located within the Ngorogoro Conservation Area (NCA), are a cornerstone for understanding the evolution of early humans and are two paleo-antropological excavation sites of global importance. NCA is located at the boundary between the Tanzanian Craton and East African Rift (EAR), in the vicinity of Ngorongoro Crater and other major volcanic edifices. Thus, understanding the geology and tectonics of the NCA may shed light onto the question why early Hominins settled in this region. Environmental and geological conditions in the Olduvai and Laetoli region that promoted human settlement and development are still debated by geologists and paleo-anthropologists. Paleo-geographical reconstructions of the study area of the last 2 million years may take advantage of modern passive seismology. Therefore, we installed a dense seismic network covering a surface of approximately 30 x 40 km within the NCA to map the depth extent of known faults, and to identify seismically active faults that have no surface expression. Our ten seismic stations, equipped with Trillium Compact 120 s sensors, started to operate in June 2016 and will continue for a total of 2 years. At the end of the first year, other 5 stations will densify our network. Here we analyse data quality of the first four months of continuous recordings. Our network provides good quality 3-C waveforms in the frequency range of 0.7-50 Hz. Vertical component seismograms record frequencies reliably down to 8 mHz. Preliminary results of the seismicity obtained with standard location procedures show that NCA is characterised by frequent tectonic seismicity (not volcano-related) with Ml between 0.5 and 2.0. Seismic activity is more frequent in the South (Laetoli region) where major fault systems have not been recognised at the surface yet.

  6. Core seismic behaviour: linear and non-linear models

    International Nuclear Information System (INIS)

    Bernard, M.; Van Dorsselaere, M.; Gauvain, M.; Jenapierre-Gantenbein, M.

    1981-08-01

    The usual methodology for the core seismic behaviour analysis leads to a double complementary approach: to define a core model to be included in the reactor-block seismic response analysis, simple enough but representative of basic movements (diagrid or slab), to define a finer core model, with basic data issued from the first model. This paper presents the history of the different models of both kinds. The inert mass model (IMM) yielded a first rough diagrid movement. The direct linear model (DLM), without shocks and with sodium as an added mass, let to two different ones: DLM 1 with independent movements of the fuel and radial blanket subassemblies, and DLM 2 with a core combined movement. The non-linear (NLM) ''CORALIE'' uses the same basic modelization (Finite Element Beams) but accounts for shocks. It studies the response of a diameter on flats and takes into account the fluid coupling and the wrapper tube flexibility at the pad level. Damping consists of one modal part of 2% and one part due to shocks. Finally, ''CORALIE'' yields the time-history of the displacements and efforts on the supports, but damping (probably greater than 2%) and fluid-structures interaction are still to be precised. The validation experiments were performed on a RAPSODIE core mock-up on scale 1, in similitude of 1/3 as to SPX 1. The equivalent linear model (ELM) was developed for the SPX 1 reactor-block response analysis and a specified seismic level (SB or SM). It is composed of several oscillators fixed to the diagrid and yields the same maximum displacements and efforts than the NLM. The SPX 1 core seismic analysis with a diagrid input spectrum which corresponds to a 0,1 g group acceleration, has been carried out with these models: some aspects of these calculations are presented here

  7. Two case studies of post-seismic regime in the Vrancea region

    International Nuclear Information System (INIS)

    Ciucu, I.; Fulga, C.

    2008-01-01

    The main geophysical conceptions regarding the tectonic seismicity of the Vrancea region are presented, with emphasis on great historical earthquakes as recorded by the Romanian Earthquake Catalogue. Their geographical and in-depth distribution is also presented, as well as their main characteristics. The post-seismic regime of two main events in Vrancea (August 1986 and May 1990) is analyzed, and Omori exponents are derived for the aftershocks distribution. One exponent agrees qualitatively with the usual range of exponents (0.8 with respect to 1), while the other exponent seems to be outside this range (0.3), possibly due to an imperfect definition of the genuine aftershocks. (authors)

  8. Identification of temporal patterns in the seismicity of Sumatra using Poisson Hidden Markov models

    Directory of Open Access Journals (Sweden)

    Katerina Orfanogiannaki

    2014-05-01

    Full Text Available On 26 December 2004 and 28 March 2005 two large earthquakes occurred between the Indo-Australian and the southeastern Eurasian plates with moment magnitudes Mw=9.1 and Mw=8.6, respectively. Complete data (mb≥4.2 of the post-1993 time interval have been used to apply Poisson Hidden Markov models (PHMMs for identifying temporal patterns in the time series of the two earthquake sequences. Each time series consists of earthquake counts, in given and constant time units, in the regions determined by the aftershock zones of the two mainshocks. In PHMMs each count is generated by one of m different Poisson processes that are called states. The series of states is unobserved and is in fact a Markov chain. The model incorporates a varying seismicity rate, it assigns a different rate to each state and it detects the changes on the rate over time. In PHMMs unobserved factors, related to the local properties of the region are considered affecting the earthquake occurrence rate. Estimation and interpretation of the unobserved sequence of states that underlie the data contribute to better understanding of the geophysical processes that take place in the region. We applied PHMMs to the time series of the two mainshocks and we estimated the unobserved sequences of states that underlie the data. The results obtained showed that the region of the 26 December 2004 earthquake was in state of low seismicity during almost the entire observation period. On the contrary, in the region of the 28 March 2005 earthquake the seismic activity is attributed to triggered seismicity, due to stress transfer from the region of the 2004 mainshock.

  9. Use of raster-based data layers to model spatial variation of seismotectonic data in probabilistic seismic hazard assessment

    Science.gov (United States)

    Zolfaghari, Mohammad R.

    2009-07-01

    Recent achievements in computer and information technology have provided the necessary tools to extend the application of probabilistic seismic hazard mapping from its traditional engineering use to many other applications. Examples for such applications are risk mitigation, disaster management, post disaster recovery planning and catastrophe loss estimation and risk management. Due to the lack of proper knowledge with regard to factors controlling seismic hazards, there are always uncertainties associated with all steps involved in developing and using seismic hazard models. While some of these uncertainties can be controlled by more accurate and reliable input data, the majority of the data and assumptions used in seismic hazard studies remain with high uncertainties that contribute to the uncertainty of the final results. In this paper a new methodology for the assessment of seismic hazard is described. The proposed approach provides practical facility for better capture of spatial variations of seismological and tectonic characteristics, which allows better treatment of their uncertainties. In the proposed approach, GIS raster-based data models are used in order to model geographical features in a cell-based system. The cell-based source model proposed in this paper provides a framework for implementing many geographically referenced seismotectonic factors into seismic hazard modelling. Examples for such components are seismic source boundaries, rupture geometry, seismic activity rate, focal depth and the choice of attenuation functions. The proposed methodology provides improvements in several aspects of the standard analytical tools currently being used for assessment and mapping of regional seismic hazard. The proposed methodology makes the best use of the recent advancements in computer technology in both software and hardware. The proposed approach is well structured to be implemented using conventional GIS tools.

  10. Hydraulic fracturing and the Crooked Lake Sequences: Insights gleaned from regional seismic networks

    Science.gov (United States)

    Schultz, Ryan; Stern, Virginia; Novakovic, Mark; Atkinson, Gail; Gu, Yu Jeffrey

    2015-04-01

    Within central Alberta, Canada, a new sequence of earthquakes has been recognized as of 1 December 2013 in a region of previous seismic quiescence near Crooked Lake, ~30 km west of the town of Fox Creek. We utilize a cross-correlation detection algorithm to detect more than 160 events to the end of 2014, which is temporally distinguished into five subsequences. This observation is corroborated by the uniqueness of waveforms clustered by subsequence. The Crooked Lake Sequences have come under scrutiny due to its strong temporal correlation (>99.99%) to the timing of hydraulic fracturing operations in the Duvernay Formation. We assert that individual subsequences are related to fracturing stimulation and, despite adverse initial station geometry, double-difference techniques allow us to spatially relate each cluster back to a unique horizontal well. Overall, we find that seismicity in the Crooked Lake Sequences is consistent with first-order observations of hydraulic fracturing induced seismicity.

  11. Air gun seismic effects on larvae and fry offshore; modeling and simulation

    International Nuclear Information System (INIS)

    Holmstroem, S.

    1993-04-01

    This report presents results from modeling and simulation of air gun seismic effects on fish and fry. A model has been developed to describe the behavior of fishes when a seismic ship is approaching and passes by the volume of residence of the fishes. The swimming capacity, the reaction to acoustic stimuli, the hearing threshold and the vertical distribution of the fishes have been included in the model. The model has been applied on cod fishes of length 25 and 350 mm. For realistic vertical distributions the big cod fishes will get away from the region near the boat where the probability for a mortal damage is greatest. 121 refs., 40 figs., 13 tabs

  12. Realistic modelling of observed seismic motion in complex sedimentary basins

    International Nuclear Information System (INIS)

    Faeh, D.; Panza, G.F.

    1994-03-01

    Three applications of a numerical technique are illustrated to model realistically the seismic ground motion for complex two-dimensional structures. First we consider a sedimentary basin in the Friuli region, and we model strong motion records from an aftershock of the 1976 earthquake. Then we simulate the ground motion caused in Rome by the 1915, Fucino (Italy) earthquake, and we compare our modelling with the damage distribution observed in the town. Finally we deal with the interpretation of ground motion recorded in Mexico City, as a consequence of earthquakes in the Mexican subduction zone. The synthetic signals explain the major characteristics (relative amplitudes, spectral amplification, frequency content) of the considered seismograms, and the space distribution of the available macroseismic data. For the sedimentary basin in the Friuli area, parametric studies demonstrate the relevant sensitivity of the computed ground motion to small changes in the subsurface topography of the sedimentary basin, and in the velocity and quality factor of the sediments. The total energy of ground motion, determined from our numerical simulation in Rome, is in very good agreement with the distribution of damage observed during the Fucino earthquake. For epicentral distances in the range 50km-100km, the source location and not only the local soil conditions control the local effects. For Mexico City, the observed ground motion can be explained as resonance effects and as excitation of local surface waves, and the theoretical and the observed maximum spectral amplifications are very similar. In general, our numerical simulations permit the estimate of the maximum and average spectral amplification for specific sites, i.e. are a very powerful tool for accurate micro-zonation. (author). 38 refs, 19 figs, 1 tab

  13. A high-resolution ambient seismic noise model for Europe

    Science.gov (United States)

    Kraft, Toni

    2014-05-01

    measurement precision (i.e. earthquake location), while considering this extremely complex boundary condition. To solve this problem I have developed a high-resolution ambient seismic noise model for Europe. The model is based on land-use data derived from satellite imagery by the EU-project CORINE in a resolution of 100x100m. The the CORINE data consists of several land-use classes, which, besides others, contain: industrial areas, mines, urban fabric, agricultural areas, permanent corps, forests and open spaces. Additionally, open GIS data for highways, and major and minor roads and railway lines were included from the OpenStreetMap project (www.openstreetmap.org). This data was divided into three classes that represent good, intermediate and bad ambient conditions of the corresponding land-use class based on expert judgment. To account for noise propagation away from its source a smoothing operator was applied to individual land-use noise-fields. Finally, the noise-fields were stacked to obtain an European map of ambient noise conditions. A calibration of this map with data of existing seismic stations Europe allowed me to estimate the expected noise level in actual ground motion units for the three ambient noise condition classes of the map. The result is a high-resolution ambient seismic noise map, that allows the network designer to make educated predictions on the expected noise level for arbitrary location in Europe. The ambient noise model was successfully tested in several network optimization projects in Switzerland and surrounding countries and will hopefully be a valuable contribution to improving the data quality of microseismic monitoring networks in Europe.

  14. Crustal deformation and seismic measurements in the region of McDonald Observatory, West Texas. [Texas and Northern Chihuahua, Mexico

    Science.gov (United States)

    Dorman, H. J.

    1981-01-01

    The arrival times of regional and local earthquakes and located earthquakes in the Basin and Range province of Texas and in the adjacent areas of Chihuahua, Mexico from January 1976 to August 1980 at the UT'NASA seismic array are summarized. The August 1931 Texas earthquake is reevaluated and the seismicity and crustal structure of West Texas is examined. A table of seismic stations is included.

  15. Distance effects on regional discriminants along a seismic profile in Northwest Nevada; NPE and nuclear results

    Energy Technology Data Exchange (ETDEWEB)

    McCormack, D.A. [AWE Blacknest, Berkshire (United Kingdom); Priestley, K.F. [Univ. of Cambridge (United Kingdom); Patton, H.J. [Lawrence Livermore National Lab., CA (United States)

    1994-12-31

    To address questions of discriminant transportability, it is important to understand how discriminants based on regional seismic phases are affected by regional variations in velocity structure. To examine this issue, we have recorded two explosions, the nuclear explosion Kinibito and the Non-Proliferation Experiment along a 300 km-long profile through western Nevada. We use these data to investigate the stability with distance of several proposed seismic discriminants. In this study we first estimate the apparent attenuation of the regional phases. We compare attenuation corrected amplitude ratios for P{sub n}/L{sub g} and P{sub g}/L{sub g}, and spectral ratios for P{sub n}, P{sub g}, and L{sub g}, as a function of distance along the profile. We make these comparisons for the vertical component and for the total vector resultant using all three components of motion.

  16. Regionalizing global climate models

    NARCIS (Netherlands)

    Pitman, A.J.; Arneth, A.; Ganzeveld, L.N.

    2012-01-01

    Global climate models simulate the Earth's climate impressively at scales of continents and greater. At these scales, large-scale dynamics and physics largely define the climate. At spatial scales relevant to policy makers, and to impacts and adaptation, many other processes may affect regional and

  17. Integration of onshore and offshore seismological data to study the seismicity of the Calabrian Region

    Science.gov (United States)

    D'Alessandro, Antonino; Guerra, Ignazio; D'Anna, Giuseppe; Gervasi, Anna; Harabaglia, Paolo; Luzio, Dario; Stellato, Gilda

    2014-05-01

    The Pollino Massif marks the transition from the Southern Appenninic to the Calabrian Arc. On the western side it is characterized by a moderately sized seismicity (about 9 M > 4 events in the last 50 years), well documented in the last 400 years. The moment tensor solutions available in this area yields, mainly, normal faults with coherent Southern Appeninic trend. This remains true also for the events that are localized on the calabrian side of Pollino, South of the massif. In most of the Sibari plane, seismic activity is very scarce, while it is again rather marked on its southeastern corner, both onshore and offshore. The above observations point to the perspective that the stress field of a vast portion of Northern Calabria still resembles that of the Southern Appenines. In this frame, it becomes important to investigate the offshore seismicity of the Sibari Gulf and the deformation pattern within the Sibari Plane. The latter might function as a hinge to transfer the deformation of the extensional fault system in the Pollino area to a different offshore fault system. Since return times of larger events might be very long, we need to investigate the true seismic potential of the offshore faults and to verify whether they are truly strike slip or if they could involve relevant thrust or normal components, that would add to the risk that of potentially associated tsunamis. Despite their importance in the understanding of the seismotectonic processes taking place in the Southern Appenninic - Calabrian Arc border and surrounding areas, the seismicity and the seismogenic volumes of the Sibari Gulf until now has not been well characterized due to the lack of offshore seismic stations. The seismicity of the Calabrian is monitored by the Italian National Seismic Network (INSN) managed by Istituto Nazionale di Geofisica e Vulcanologia and by the Calabrian Regional Seismic Network (CRSN) managed by the University of Calabria. Both the network comprise only on

  18. Acoustic/seismic signal propagation and sensor performance modeling

    Science.gov (United States)

    Wilson, D. Keith; Marlin, David H.; Mackay, Sean

    2007-04-01

    Performance, optimal employment, and interpretation of data from acoustic and seismic sensors depend strongly and in complex ways on the environment in which they operate. Software tools for guiding non-expert users of acoustic and seismic sensors are therefore much needed. However, such tools require that many individual components be constructed and correctly connected together. These components include the source signature and directionality, representation of the atmospheric and terrain environment, calculation of the signal propagation, characterization of the sensor response, and mimicking of the data processing at the sensor. Selection of an appropriate signal propagation model is particularly important, as there are significant trade-offs between output fidelity and computation speed. Attenuation of signal energy, random fading, and (for array systems) variations in wavefront angle-of-arrival should all be considered. Characterization of the complex operational environment is often the weak link in sensor modeling: important issues for acoustic and seismic modeling activities include the temporal/spatial resolution of the atmospheric data, knowledge of the surface and subsurface terrain properties, and representation of ambient background noise and vibrations. Design of software tools that address these challenges is illustrated with two examples: a detailed target-to-sensor calculation application called the Sensor Performance Evaluator for Battlefield Environments (SPEBE) and a GIS-embedded approach called Battlefield Terrain Reasoning and Awareness (BTRA).

  19. Ground magnetic studies along a regional seismic-reflection profile across Bare Mountain, Crater Flat and Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Langenheim, V.E.; Ponce, D.A.

    1995-01-01

    Ground magnetic data were collected along a 26-km-long regional seismic-reflection profile in southwest Nevada that starts in the Amargosa Desert, crosses Bare Mountain, Crater Flat and Yucca Mountain, and ends in Midway Valley. Parallel ground magnetic profiles were also collected about 100 m to either side of the western half of the seismic-reflection line. The magnetic data indicate that the eastern half of Crater Flat is characterized by closely-spaced faulting (1--2 km) in contrast to the western half of Crater Flat. Modeling of the data indicates that the Topopah Spring Tuff is offset about 250 m on the Solitario Canyon fault and about 50 m on the Ghost Dance fault. These estimates of fault offset are consistent with seismic-reflection data and geologic mapping. A broad magnetic high of about 500--600 nT is centered over Crater Flat. Modeling of the magnetic data indicates that the source of this high is not thickening and doming of the Bullfrog Tuff, but more likely lies below the Bullfrog Tuff. Possible source lithologies for this magnetic high include altered argillite of the Eleana Formation, Cretaceous or Tertiary intrusions, and mafic sills

  20. Improving fault image by determination of optimum seismic survey parameters using ray-based modeling

    Science.gov (United States)

    Saffarzadeh, Sadegh; Javaherian, Abdolrahim; Hasani, Hossein; Talebi, Mohammad Ali

    2018-06-01

    In complex structures such as faults, salt domes and reefs, specifying the survey parameters is more challenging and critical owing to the complicated wave field behavior involved in such structures. In the petroleum industry, detecting faults has become crucial for reservoir potential where faults can act as traps for hydrocarbon. In this regard, seismic survey modeling is employed to construct a model close to the real structure, and obtain very realistic synthetic seismic data. Seismic modeling software, the velocity model and parameters pre-determined by conventional methods enable a seismic survey designer to run a shot-by-shot virtual survey operation. A reliable velocity model of structures can be constructed by integrating the 2D seismic data, geological reports and the well information. The effects of various survey designs can be investigated by the analysis of illumination maps and flower plots. Also, seismic processing of the synthetic data output can describe the target image using different survey parameters. Therefore, seismic modeling is one of the most economical ways to establish and test the optimum acquisition parameters to obtain the best image when dealing with complex geological structures. The primary objective of this study is to design a proper 3D seismic survey orientation to achieve fault zone structures through ray-tracing seismic modeling. The results prove that a seismic survey designer can enhance the image of fault planes in a seismic section by utilizing the proposed modeling and processing approach.

  1. Time-predictable model application in probabilistic seismic hazard analysis of faults in Taiwan

    Directory of Open Access Journals (Sweden)

    Yu-Wen Chang

    2017-01-01

    Full Text Available Given the probability distribution function relating to the recurrence interval and the occurrence time of the previous occurrence of a fault, a time-dependent model of a particular fault for seismic hazard assessment was developed that takes into account the active fault rupture cyclic characteristics during a particular lifetime up to the present time. The Gutenberg and Richter (1944 exponential frequency-magnitude relation uses to describe the earthquake recurrence rate for a regional source. It is a reference for developing a composite procedure modelled the occurrence rate for the large earthquake of a fault when the activity information is shortage. The time-dependent model was used to describe the fault characteristic behavior. The seismic hazards contribution from all sources, including both time-dependent and time-independent models, were then added together to obtain the annual total lifetime hazard curves. The effects of time-dependent and time-independent models of fault [e.g., Brownian passage time (BPT and Poisson, respectively] in hazard calculations are also discussed. The proposed fault model result shows that the seismic demands of near fault areas are lower than the current hazard estimation where the time-dependent model was used on those faults, particularly, the elapsed time since the last event of the faults (such as the Chelungpu fault are short.

  2. Recent crustal movements and seismicity in the western coastal region of peninsular India

    Science.gov (United States)

    Kailasam, L. N.

    1983-09-01

    Recent crustal movements, tectonics and seismicity of the western coastal region of peninsular India have been studied in detail in the very recent past. Prominent geomorphic features and large-scale manifestation of Holocene deformation and crustal movements have been noticed and studied over this coastal region from the Gulf of Cambay to the southernmost parts of Kerala, evidence for which is afforded in the form of Recent and sub-Recent raised beaches, sandbars, raised old terraces, pebble beds, etc. The sedimentary formations in this narrow coastal belt include Neogene and Quaternary sediments. The Bouguer gravity map of the western coastal tract shows some prominent gravity features extending into the offshore regions, suggestive of some significant tectonic and structural features. The seismic data in the offshore regions bring out some prominent roughly northwest-southeast as well as east-west faults and shears, in addition to prominent structural "highs" off the Bombay and Ratnagiri coast which have proved oil. The seismicity in this coastal tract as well as the faulted western margin of the western continental shelf in the Arabian Sea is generally of magnitude 3-6.

  3. Realistic Modeling of Seismic Wave Ground Motion in Beijing City

    Science.gov (United States)

    Ding, Z.; Romanelli, F.; Chen, Y. T.; Panza, G. F.

    Algorithms for the calculation of synthetic seismograms in laterally heterogeneous anelastic media have been applied to model the ground motion in Beijing City. The synthetic signals are compared with the few available seismic recordings (1998, Zhangbei earthquake) and with the distribution of observed macroseismic intensity (1976, Tangshan earthquake). The synthetic three-component seismograms have been computed for the Xiji area and Beijing City. The numerical results show that the thick Tertiary and Quaternary sediments are responsible for the severe amplification of the seismic ground motion. Such a result is well correlated with the abnormally high macroseismic intensity zone in the Xiji area associated with the 1976 Tangshan earthquake as well as with the ground motion recorded in Beijing city in the wake of the 1998 Zhangbei earthquake.

  4. Realistic modeling of seismic wave ground motion in Beijing City

    International Nuclear Information System (INIS)

    Ding, Z.; Chen, Y.T.; Romanelli, F.; Panza, G.F.

    2002-05-01

    Advanced algorithms for the calculation of synthetic seismograms in laterally heterogeneous anelastic media have been applied to model the ground motion in Beijing City. The synthetic signals are compared with the few available seismic recordings (1998, Zhangbei earthquake) and with the distribution of the observed macroseismic intensity (1976, Tangshan earthquake). The synthetic 3-component seismograms have been computed in the Xiji area and in Beijing town. The numerical results show that the thick Tertiary and Quaternary sediments are responsible of the severe amplification of the seismic ground motion. Such a result is well correlated with the abnormally high macroseismic intensity zone (Xiji area) associated to the 1976 Tangshan earthquake and with the records in Beijing town, associated to the 1998 Zhangbei earthquake. (author)

  5. A hierarchical stress release model for synthetic seismicity

    Science.gov (United States)

    Bebbington, Mark

    1997-06-01

    We construct a stochastic dynamic model for synthetic seismicity involving stochastic stress input, release, and transfer in an environment of heterogeneous strength and interacting segments. The model is not fault-specific, having a number of adjustable parameters with physical interpretation, namely, stress relaxation, stress transfer, stress dissipation, segment structure, strength, and strength heterogeneity, which affect the seismicity in various ways. Local parameters are chosen to be consistent with large historical events, other parameters to reproduce bulk seismicity statistics for the fault as a whole. The one-dimensional fault is divided into a number of segments, each comprising a varying number of nodes. Stress input occurs at each node in a simple random process, representing the slow buildup due to tectonic plate movements. Events are initiated, subject to a stochastic hazard function, when the stress on a node exceeds the local strength. An event begins with the transfer of excess stress to neighboring nodes, which may in turn transfer their excess stress to the next neighbor. If the event grows to include the entire segment, then most of the stress on the segment is transferred to neighboring segments (or dissipated) in a characteristic event. These large events may themselves spread to other segments. We use the Middle America Trench to demonstrate that this model, using simple stochastic stress input and triggering mechanisms, can produce behavior consistent with the historical record over five units of magnitude. We also investigate the effects of perturbing various parameters in order to show how the model might be tailored to a specific fault structure. The strength of the model lies in this ability to reproduce the behavior of a general linear fault system through the choice of a relatively small number of parameters. It remains to develop a procedure for estimating the internal state of the model from the historical observations in order to

  6. Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity

    Science.gov (United States)

    Uyeda, S.; Nagao, T.; Hattori, K.; Hayakawa, M.; Miyaki, K.; Molchanov, O.; Gladychev, V.; Baransky, L.; Chtchekotov, A.; Fedorov, E.; Pokhotelov, O.; Andreevsky, S.; Rozhnoi, A.; Khabazin, Y.; Gorbatikov, A.; Gordeev, E.; Chebrov, V.; Sinitzin, V.; Lutikov, A.; Yunga, S.; Kosarev, G.; Surkov, V.; Belyaev, G.

    Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity). The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 - 40 Hz) and meteorological recordings, together with seismo-acoustic (∆F = 30 - 1000 Hz) and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 - 30 Hz), three-component electric potential variations ( ∆F < 1.0 Hz), and VLF transmitter's signal perturbations ( ∆F ~ 10 - 40 kHz).

  7. Geophysical Observatory in Kamchatka region for monitoring of phenomena connected with seismic activity

    Directory of Open Access Journals (Sweden)

    S. Uyeda

    2001-01-01

    Full Text Available Regular monitoring of some geophysical parameters in association with seismicity has been carried out since last year at the Japan-Russian Complex Geophysical Observatory in the Kamchatka region. This observatory was organized in connection with the ISTC project in Russia and was motivated by the results of the FRONTIER/RIKEN and FRONTIER/NASDA research projects in Japan. The main purpose of the observations is to investigate the electromagnetic and acoustic phenomena induced by the lithosphere processes (especially by seismic activity. The seismicity of the Kamchatka area is analyzed and a description of the observatory equipment is presented. At present, the activity of the observatory includes the seismic (frequency range ∆F = 0.5 – 40 Hz and meteorological recordings, together with seismo-acoustic (∆F = 30 – 1000 Hz and electromagnetic observations: three-component magnetic ULF variations ( ∆F = 0.003 – 30 Hz, three-component electric potential variations ( ∆F 1.0 Hz, and VLF transmitter’s signal perturbations ( ∆F ~ 10 – 40 kHz.

  8. Radon variations in active volcanoes and in regions with high seismicity: internal and external factors

    International Nuclear Information System (INIS)

    Segovia, N.; Cruz-Reyna, S. De la; Mena, M.

    1986-01-01

    The results of 4 years of observations of radon concentrations in soils of active volcanoes of Costa Rica and a highly seismic region in Mexico are discussed. A distinction is made between the influences of external (mostly meteorological) and internal (magmatic or tectonic) factors on the variation in radon levels. The geological meaning of the radon data can be thus enhanced if the external factors are excluded. (author)

  9. Preliminary Interpretations of Multi-Channel Seismic Reflection and Magnetic Data on North Anatolian Fault (NAF) in the Eastern Marmara Region, Turkey

    Science.gov (United States)

    Gözde Okut Toksoy, Nigar; Kurt, Hülya; İşseven, Turgay

    2017-04-01

    The North Anatolian Fault (NAF) is 1600 km long, right lateral strike-slip fault nearly E-W elongated between Karlıova in the east and Saros Gulf in the west. NAF splays into two major strands near the west of Bolu city as Northern and Southern strands. Northern strand passes Sapanca Lake and extends towards west and reaches Marmara Sea through the Gulf of Izmit. The area has high seismicity; 1999 Kocaeli (Mw=7.4) and 1999 Düzce (Mw=7.2) earthquakes caused approximately 150 km long surface rupture between the Gulf of Izmit and Bolu. The rupture has four distinct fault segments as Gölcük, Sapanca, Sakarya, and Karadere from west to east. In this study multi-channel seismic and magnetic data are collected for the first time on the Sapanca Segment to investigate the surficial and deeper geometry of the NAF. Previously, the NAF in the eastern Marmara region is investigated using by paleo-seismological data from trenches on the surface rupture of fault or the geomorphological data (Lettis et al., 2000; Dikbaş and Akyüz, 2010) which have shallower depth targets. Crustal structure and seismic velocities for Central Anatolia and eastern Marmara regions are obtained from deeper targeted refraction data (Gürbüz et al., 1992). However, their velocity models do not have the spatial resolution to determine details of the fault zone structure. Multi-channel seismic and magnetic data in this study were acquired on two N-S directed profiles crossing NAF perpendicularly near Kartepe on the western part of the Sapanca Lake in October 2016. The receiver interval is 5 m, shot interval is 5-10 m, and the total length of the profiles are approximately 1400 m. Buffalo Gun is used as a seismic source for deeper penetration. Conventional seismic reflection processing steps are applied to the data. These are geometry definition, editing, filtering, static correction, velocity analysis and deconvolution, stacking and migration. Echos seismic software package in Geophysical Department

  10. A modified symplectic PRK scheme for seismic wave modeling

    Science.gov (United States)

    Liu, Shaolin; Yang, Dinghui; Ma, Jian

    2017-02-01

    A new scheme for the temporal discretization of the seismic wave equation is constructed based on symplectic geometric theory and a modified strategy. The ordinary differential equation in terms of time, which is obtained after spatial discretization via the spectral-element method, is transformed into a Hamiltonian system. A symplectic partitioned Runge-Kutta (PRK) scheme is used to solve the Hamiltonian system. A term related to the multiplication of the spatial discretization operator with the seismic wave velocity vector is added into the symplectic PRK scheme to create a modified symplectic PRK scheme. The symplectic coefficients of the new scheme are determined via Taylor series expansion. The positive coefficients of the scheme indicate that its long-term computational capability is more powerful than that of conventional symplectic schemes. An exhaustive theoretical analysis reveals that the new scheme is highly stable and has low numerical dispersion. The results of three numerical experiments demonstrate the high efficiency of this method for seismic wave modeling.

  11. Monitoring of seismic events from a specific source region using a single regional array: A case study

    Science.gov (United States)

    Gibbons, S. J.; Kværna, T.; Ringdal, F.

    2005-07-01

    In the monitoring of earthquakes and nuclear explosions using a sparse worldwide network of seismic stations, it is frequently necessary to make reliable location estimates using a single seismic array. It is also desirable to screen out routine industrial explosions automatically in order that analyst resources are not wasted upon detections which can, with a high level of confidence, be associated with such a source. The Kovdor mine on the Kola Peninsula of NW Russia is the site of frequent industrial blasts which are well recorded by the ARCES regional seismic array at a distance of approximately 300 km. We describe here an automatic procedure for identifying signals which are likely to result from blasts at the Kovdor mine and, wherever possible, for obtaining single array locations for such events. Carefully calibrated processing parameters were chosen using measurements from confirmed events at the mine over a one-year period for which the operators supplied Ground Truth information. Phase arrival times are estimated using an autoregressive method and slowness and azimuth are estimated using broadband f{-} k analysis in fixed frequency bands and time-windows fixed relative to the initial P-onset time. We demonstrate the improvement to slowness estimates resulting from the use of fixed frequency bands. Events can be located using a single array if, in addition to the P-phase, at least one secondary phase is found with both an acceptable slowness estimate and valid onset-time estimate. We evaluate the on-line system over a twelve month period; every event known to have occured at the mine is detected by the process and 32 out of 53 confirmed events were located automatically. The remaining events were classified as “very likely” Kovdor events and were subsequently located by an analyst. The false alarm rate is low; only 84 very likely Kovdor events were identified during the whole of 2003 and none of these were subsequently located at a large distance from

  12. Detecting Seismic Events Using a Supervised Hidden Markov Model

    Science.gov (United States)

    Burks, L.; Forrest, R.; Ray, J.; Young, C.

    2017-12-01

    We explore the use of supervised hidden Markov models (HMMs) to detect seismic events in streaming seismogram data. Current methods for seismic event detection include simple triggering algorithms, such as STA/LTA and the Z-statistic, which can lead to large numbers of false positives that must be investigated by an analyst. The hypothesis of this study is that more advanced detection methods, such as HMMs, may decreases false positives while maintaining accuracy similar to current methods. We train a binary HMM classifier using 2 weeks of 3-component waveform data from the International Monitoring System (IMS) that was carefully reviewed by an expert analyst to pick all seismic events. Using an ensemble of simple and discrete features, such as the triggering of STA/LTA, the HMM predicts the time at which transition occurs from noise to signal. Compared to the STA/LTA detection algorithm, the HMM detects more true events, but the false positive rate remains unacceptably high. Future work to potentially decrease the false positive rate may include using continuous features, a Gaussian HMM, and multi-class HMMs to distinguish between types of seismic waves (e.g., P-waves and S-waves). Acknowledgement: Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.SAND No: SAND2017-8154 A

  13. Combined Gravimetric-Seismic Crustal Model for Antarctica

    Science.gov (United States)

    Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad

    2018-01-01

    The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24

  14. A SEISMIC DESIGN OF NUCLEAR REACTOR BUILDING STRUCTURES APPLYING SEISMIC ISOLATION SYSTEM IN A HIGH SEISMICITY REGION –A FEASIBILITY CASE STUDY IN JAPAN-

    Directory of Open Access Journals (Sweden)

    TETSUO KUBO

    2014-10-01

    Full Text Available A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation system is introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widely employed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied to NPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildings in Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearings with a lead plug positioned (LRB is examined. Through a series of seismic response analyses using the so-named standard design earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responses of the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1 the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2 the responses obtained for the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of the design-basis; and (3 the responses of isolated reactor building fall below the range of the prescribed criteria.

  15. A seismic design of nuclear reactor building structures applying seismic isolation system in a seismicity region-a feasibility case study in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Tetsuo [The University of Tokyo, Tokyo (Japan); Yamamoto, Tomofumi; Sato, Kunihiko [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Jimbo, Masakazu [Toshiba Corporation, Yokohama (Japan); Imaoka, Tetsuo [Hitachi-GE Nuclear Energy, Ltd., Hitachi (Japan); Umeki, Yoshito [Chubu Electric Power Co. Inc., Nagoya (Japan)

    2014-10-15

    A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation system is introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widely employed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied to NPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildings in Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearings with a lead plug positioned (LRB) is examined. Through a series of seismic response analyses using the so-named standard design earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responses of the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1) the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2) the responses obtained for the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of the design-basis; and (3) the responses of isolated reactor building fall below the range of the prescribed criteria.

  16. Seismic assessment and performance of nonstructural components affected by structural modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hur, Jieun; Althoff, Eric; Sezen, Halil; Denning, Richard; Aldemir, Tunc [Ohio State University, Columbus (United States)

    2017-03-15

    Seismic probabilistic risk assessment (SPRA) requires a large number of simulations to evaluate the seismic vulnerability of structural and nonstructural components in nuclear power plants. The effect of structural modeling and analysis assumptions on dynamic analysis of 3D and simplified 2D stick models of auxiliary buildings and the attached nonstructural components is investigated. Dynamic characteristics and seismic performance of building models are also evaluated, as well as the computational accuracy of the models. The presented results provide a better understanding of the dynamic behavior and seismic performance of auxiliary buildings. The results also help to quantify the impact of uncertainties associated with modeling and analysis of simplified numerical models of structural and nonstructural components subjected to seismic shaking on the predicted seismic failure probabilities of these systems.

  17. A California statewide three-dimensional seismic velocity model from both absolute and differential times

    Science.gov (United States)

    Lin, G.; Thurber, C.H.; Zhang, H.; Hauksson, E.; Shearer, P.M.; Waldhauser, F.; Brocher, T.M.; Hardebeck, J.

    2010-01-01

    We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP=VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE directionand 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling.

  18. A Gravity data along LARSE (Los Angeles Regional Seismic Experiment) Line II, Southern California

    Science.gov (United States)

    Wooley, R.J.; Langenheim, V.E.

    2001-01-01

    The U.S. Geological Survey conducted a detailed gravity study along part of the Los Angeles Regional Seismic Experiment (LARSE) transect across the San Fernando Basin and Transverse Ranges to help characterize the structure underlying this area. 249 gravity measurements were collected along the transect and to augment regional coverage near the profile. An isostatic gravity low of 50-60 mGal reflects the San Fernando-East Ventura basin. Another prominent isostatic gravity with an amplitude of 30 mGal marks the Antelope Valley basin. Gravity highs occur over the Santa Monica Mountains and the Transverse Ranges. The highest isostatic gravity values coincide with outcrops of Pelona schist.

  19. Seismic Full Waveform Modeling & Imaging in Attenuating Media

    Science.gov (United States)

    Guo, Peng

    Seismic attenuation strongly affects seismic waveforms by amplitude loss and velocity dispersion. Without proper inclusion of Q parameters, errors can be introduced for seismic full waveform modeling and imaging. Three different (Carcione's, Robertsson's, and the generalized Robertsson's) isotropic viscoelastic wave equations based on the generalized standard linear solid (GSLS) are evaluated. The second-order displacement equations are derived, and used to demonstrate that, with the same stress relaxation times, these viscoelastic formulations are equivalent. By introducing separate memory variables for P and S relaxation functions, Robertsson's formulation is generalized to allow different P and S wave stress relaxation times, which improves the physical consistency of the Qp and Qs modelled in the seismograms.The three formulations have comparable computational cost. 3D seismic finite-difference forward modeling is applied to anisotropic viscoelastic media. The viscoelastic T-matrix (a dynamic effective medium theory) relates frequency-dependent anisotropic attenuation and velocity to reservoir properties in fractured HTI media, based on the meso-scale fluid flow attenuation mechanism. The seismic signatures resulting from changing viscoelastic reservoir properties are easily visible. Analysis of 3D viscoelastic seismograms suggests that anisotropic attenuation is a potential tool for reservoir characterization. To compensate the Q effects during reverse-time migration (RTM) in viscoacoustic and viscoelastic media, amplitudes need to be compensated during wave propagation; the propagation velocity of the Q-compensated wavefield needs to be the same as in the attenuating wavefield, to restore the phase information. Both amplitude and phase can be compensated when the velocity dispersion and the amplitude loss are decoupled. For wave equations based on the GSLS, because Q effects are coupled in the memory variables, Q-compensated wavefield propagates faster than

  20. Numerical modeling of intraplate seismicity with a deformable loading plate

    Science.gov (United States)

    So, B. D.; Capitanio, F. A.

    2017-12-01

    We use finite element modeling to investigate on the stress loading-unloading cycles and earthquakes occurrence in the plate interiors, resulting from the interactions of tectonic plates along their boundary. We model a visco-elasto-plastic plate embedding a single or multiple faults, while the tectonic stress is applied along the plate boundary by an external loading visco-elastic plate, reproducing the tectonic setting of two interacting lithospheres. Because the two plates deform viscously, the timescale of stress accumulation and release on the faults is self-consistently determined, from the boundary to the interiors, and seismic recurrence is an emerging feature. This approach overcomes the constraints on recurrence period imposed by stress (stress-drop) and velocity boundary conditions, while here it is unconstrained. We illustrate emerging macroscopic characteristics of this system, showing that the seismic recurrence period τ becomes shorter as Γ and Θ decreases, where Γ = ηI/ηL the viscosity ratio of the viscosities of the internal fault-embedded to external loading plates, respectively, and Θ = σY/σL the stress ratio of the elastic limit of the fault to far-field loading stress. When the system embeds multiple, randomly distributed faults, stress transfer results in recurrence period deviations, however the time-averaged recurrence period of each fault show the same dependence on Γ and Θ, illustrating a characteristic collective behavior. The control of these parameters prevails even when initial pre-stress was randomly assigned in terms of the spatial arrangement and orientation on the internal plate, mimicking local fluctuations. Our study shows the relevance of macroscopic rheological properties of tectonic plates on the earthquake occurrence in plate interiors, as opposed to local factors, proposing a viable model for the seismic behavior of continent interiors in the context of large-scale, long-term deformation of interacting tectonic

  1. Do French macroseismic intensity observations agree with expectations from the European Seismic Hazard Model 2013?

    Science.gov (United States)

    Rey, Julien; Beauval, Céline; Douglas, John

    2018-02-01

    Probabilistic seismic hazard assessments are the basis of modern seismic design codes. To test fully a seismic hazard curve at the return periods of interest for engineering would require many thousands of years' worth of ground-motion recordings. Because strong-motion networks are often only a few decades old (e.g. in mainland France the first accelerometric network dates from the mid-1990s), data from such sensors can be used to test hazard estimates only at very short return periods. In this article, several hundreds of years of macroseismic intensity observations for mainland France are interpolated using a robust kriging-with-a-trend technique to establish the earthquake history of every French mainland municipality. At 24 selected cities representative of the French seismic context, the number of exceedances of intensities IV, V and VI is determined over time windows considered complete. After converting these intensities to peak ground accelerations using the global conversion equation of Caprio et al. (Ground motion to intensity conversion equations (GMICEs): a global relationship and evaluation of regional dependency, Bulletin of the Seismological Society of America 105:1476-1490, 2015), these exceedances are compared with those predicted by the European Seismic Hazard Model 2013 (ESHM13). In half of the cities, the number of observed exceedances for low intensities (IV and V) is within the range of predictions of ESHM13. In the other half of the cities, the number of observed exceedances is higher than the predictions of ESHM13. For intensity VI, the match is closer, but the comparison is less meaningful due to a scarcity of data. According to this study, the ESHM13 underestimates hazard in roughly half of France, even when taking into account the uncertainty in the conversion from intensity to acceleration. However, these results are valid only for the acceleration range tested in this study (0.01 to 0.09 g).

  2. Do French macroseismic intensity observations agree with expectations from the European Seismic Hazard Model 2013?

    Science.gov (United States)

    Rey, Julien; Beauval, Céline; Douglas, John

    2018-05-01

    Probabilistic seismic hazard assessments are the basis of modern seismic design codes. To test fully a seismic hazard curve at the return periods of interest for engineering would require many thousands of years' worth of ground-motion recordings. Because strong-motion networks are often only a few decades old (e.g. in mainland France the first accelerometric network dates from the mid-1990s), data from such sensors can be used to test hazard estimates only at very short return periods. In this article, several hundreds of years of macroseismic intensity observations for mainland France are interpolated using a robust kriging-with-a-trend technique to establish the earthquake history of every French mainland municipality. At 24 selected cities representative of the French seismic context, the number of exceedances of intensities IV, V and VI is determined over time windows considered complete. After converting these intensities to peak ground accelerations using the global conversion equation of Caprio et al. (Ground motion to intensity conversion equations (GMICEs): a global relationship and evaluation of regional dependency, Bulletin of the Seismological Society of America 105:1476-1490, 2015), these exceedances are compared with those predicted by the European Seismic Hazard Model 2013 (ESHM13). In half of the cities, the number of observed exceedances for low intensities (IV and V) is within the range of predictions of ESHM13. In the other half of the cities, the number of observed exceedances is higher than the predictions of ESHM13. For intensity VI, the match is closer, but the comparison is less meaningful due to a scarcity of data. According to this study, the ESHM13 underestimates hazard in roughly half of France, even when taking into account the uncertainty in the conversion from intensity to acceleration. However, these results are valid only for the acceleration range tested in this study (0.01 to 0.09 g).

  3. Regional seismic observations of the Non-Proliferation Experiment at the Livermore NTS Network

    Energy Technology Data Exchange (ETDEWEB)

    Walter, W.R.; Mayeda, K.; Patton, H.J. [Lawrence Livermore National Lab., CA (United States)] [and others

    1994-12-31

    The Non-Proliferation Experiment (NPE), a 1-kiloton chemical explosion in N-tunnel at Rainier Mesa on the Nevada Test Site (NTS), was recorded by the four station, regional seismic Livermore NTS Network, (LNN). In this study we compare the NPE`s seismic yield, frequency content, and discrimination performance with other NTS events recorded at LNN. Preliminary findings include: The NPE LNN average magnitudes are 4.16 for m{sub b}(P{sub n}) and 4.59 for m{sub b}(L{sub g}). Using published magnitude-yield relations gives nuclear equivalent yields of 2.3 and 2.2 kilotons respectively, implying enhanced coupling of chemical relative to nuclear explosions. A comparison of the NPE seismograms with those with similar magnitude N-tunnel nuclear explosions shows remarkable similarity over the frequency band 0.5 to 5.0 Hz. Outside this band the explosions show more variability, with the NPE having the least relative energy below 0.5 Hz and the most energy above 5 Hz when scaled by magnitude. Considering the variability within the N-tunnel nuclear explosions, these low- and high-frequency NPE-nuclear differences may not reflect chemical-nuclear source differences. The NPE was compared to a large number of NTS nuclear explosions and earthquakes as part of an ongoing short-period discrimination study of P{sub N}/L{sub g},P{sub g}/L{sub g}, and spectral ratios in the P{sub n}, P{sub g},L{sub g}, and coda phases. For these discriminants, the NPE looks very similar to N-tunnel nuclear explosions and other NTS nuclear explosions, implying seismic identification of contained, non-ripple-fired, chemical explosions as non-nuclear may not be possible. However, such blasts might serve as surrogate nuclear explosions when calibrating seismic discriminants in regions where nuclear testing has not occurred.

  4. Combined reservoir simulation and seismic technology, a new approach for modeling CHOPS

    Energy Technology Data Exchange (ETDEWEB)

    Aghabarati, H.; Lines, L.; Settari, A. [Calgary Univ., AB (Canada); Dumitrescu, C. [Sensor Geophysical Ltd., Calgary, AB (Canada)

    2008-10-15

    One of the primary recovery schemes for developing heavy oil reservoirs in Canada is cold heavy oil production with sand (CHOPS). With the introduction of progressive cavity pumps, CHOPS can be applied in unconsolidated or weakly consolidated formations. In order to better understand reservoir properties and recovery mechanism, this paper discussed the use of a combined reservoir simulation and seismic technology that were applied for a heavy oil reservoir situated in Saskatchewan, Canada. Using a seismic survey acquired in 1989, the study used geostatistical methods to estimate the initial reservoir porosity. Sand production was then modeled using an erosional velocity approach and the model was run based on oil production. The paper also compared the results of true porosity derived from simulation against the porosity estimated from a second seismic survey acquired in 2001. Last, the extent and the shape of the enhanced permeability region was modelled in order to estimate porosity distribution. It was concluded that the performance of the CHOPS wells depended greatly on the rate of creation of the high permeability zone around the wells. 9 refs., 2 tabs., 18 figs., 1 appendix.

  5. The seismic cycle at subduction thrusts: 2. Dynamic implications of geodynamic simulations validated with laboratory models

    KAUST Repository

    van Dinther, Y.

    2013-04-01

    The physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space. To investigate subduction zone dynamics and associated interplate seismicity, we validate a continuum, visco-elasto-plastic numerical model with a new laboratory approach (Paper 1). The analogous laboratory setup includes a visco-elastic gelatin wedge underthrusted by a rigid plate with defined velocity-weakening and -strengthening regions. Our geodynamic simulation approach includes velocity-weakening friction to spontaneously generate a series of fast frictional instabilities that correspond to analog earthquakes. A match between numerical and laboratory source parameters is obtained when velocity-strengthening is applied in the aseismic regions to stabilize the rupture. Spontaneous evolution of absolute stresses leads to nucleation by coalescence of neighboring patches, mainly occurring at evolving asperities near the seismogenic zone limits. Consequently, a crack-, or occasionally even pulse-like, rupture propagates toward the opposite side of the seismogenic zone by increasing stresses ahead of its rupture front, until it arrests on a barrier. The resulting surface displacements qualitatively agree with geodetic observations and show landward and, from near the downdip limit, upward interseismic motions. These are rebound and reversed coseismically. This slip increases adjacent stresses, which are relaxed postseismically by afterslip and thereby produce persistent seaward motions. The wide range of observed physical phenomena, including back-propagation and repeated slip, and the agreement with laboratory results demonstrate that visco-elasto-plastic geodynamic models with rate-dependent friction form a new tool that can greatly contribute to our understanding of the seismic cycle at subduction zones.

  6. The seismic cycle at subduction thrusts: 2. Dynamic implications of geodynamic simulations validated with laboratory models

    KAUST Repository

    van Dinther, Y.; Gerya, T. V.; Dalguer, L. A.; Corbi, F.; Funiciello, F.; Mai, Paul Martin

    2013-01-01

    The physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space. To investigate subduction zone dynamics and associated interplate seismicity, we validate a continuum, visco-elasto-plastic numerical model with a new laboratory approach (Paper 1). The analogous laboratory setup includes a visco-elastic gelatin wedge underthrusted by a rigid plate with defined velocity-weakening and -strengthening regions. Our geodynamic simulation approach includes velocity-weakening friction to spontaneously generate a series of fast frictional instabilities that correspond to analog earthquakes. A match between numerical and laboratory source parameters is obtained when velocity-strengthening is applied in the aseismic regions to stabilize the rupture. Spontaneous evolution of absolute stresses leads to nucleation by coalescence of neighboring patches, mainly occurring at evolving asperities near the seismogenic zone limits. Consequently, a crack-, or occasionally even pulse-like, rupture propagates toward the opposite side of the seismogenic zone by increasing stresses ahead of its rupture front, until it arrests on a barrier. The resulting surface displacements qualitatively agree with geodetic observations and show landward and, from near the downdip limit, upward interseismic motions. These are rebound and reversed coseismically. This slip increases adjacent stresses, which are relaxed postseismically by afterslip and thereby produce persistent seaward motions. The wide range of observed physical phenomena, including back-propagation and repeated slip, and the agreement with laboratory results demonstrate that visco-elasto-plastic geodynamic models with rate-dependent friction form a new tool that can greatly contribute to our understanding of the seismic cycle at subduction zones.

  7. New Ground Motion Prediction Models for Caucasus Region

    Science.gov (United States)

    Jorjiashvili, N.

    2012-12-01

    The Caucasus is a region of numerous natural hazards and ensuing disasters. Analysis of the losses due to past disasters indicates the those most catastrophic in the region have historically been due to strong earthquakes. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration because this parameter gives useful information for Seismic Hazard Assessment. Because of this, many peak ground acceleration attenuation relations have been developed by different authors. Besides, a few attenuation relations were developed for Caucasus region: Ambraseys et al. (1996,2005) which were based on entire European region and they were not focused locally on Caucasus Region; Smit et.al. (2000) that was based on a small amount of acceleration data that really is not enough. Since 2003 construction of Georgian Digital Seismic Network has started with the help of number of International organizations, Projects and Private companies. The works conducted involved scientific as well as organizational activities: Resolving technical problems concerning communication and data transmission. Thus, today we have a possibility to get real time data and make scientific research based on digital seismic data. Generally, ground motion and damage are influenced by the magnitude of the earthquake, the distance from the seismic source to site, the local ground conditions and the characteristics of buildings. Estimation of expected ground motion is a fundamental earthquake hazard assessment. This is the reason why this topic is emphasized in this study. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models are obtained by classical, statistical way, regression analysis. Also site ground conditions are considered because the same earthquake recorded at the same distance may cause different damage

  8. A new tomographic image on the Philippine Sea Slab beneath Tokyo - Implication to seismic hazard in the Tokyo metropolitan region -

    Science.gov (United States)

    Hirata, N.; Sakai, S.; Nakagawa, S.; Ishikawa, M.; Sato, H.; Kasahara, K.; Kimura, H.; Honda, R.

    2012-12-01

    In central Japan, the Philippine Sea plate (PSP) subducts beneath the Tokyo metropolitan region. Devastating M8-class earthquakes occurred on the upper surface of the Philippine Sea plate (SPS), examples of which are the Genroku earthquake of 1703 (magnitude M=8.0) and the Kanto earthquake of 1923 (M=7.9), which had 105,000 fatalities. A M7 or greater (M7+) earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions although it is smaller than the megathrust type M8-class earthquakes. This great earthquake is evaluated to occur with a probability of 70 % in 30 years by the Earthquake Research Committee of Japan. The M7+ earthquakes may occur either on the upper surface or intra slab of PSP. The Central Disaster Management Council of Japan estimates the next great M7+ earthquake will cause 11,000 fatalities and 112 trillion yen (1 trillion US$) economic loss at worst case if it occur beneath northern Tokyo bay with M7.3. However, the estimate is based on a source fault model by conventional studies about the PSP geometry. To evaluate seismic hazard due to the great quake we need to clarify the geometry of PSP and also the Pacific palate (PAP) that subducs beneath PSP. We identify those plates with use of seismic tomography and available deep seismic reflection profiling and borehole data in southern Kanto area. We deployed about 300 seismic stations in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area. We obtain clear P- and S- wave velocity (Vp and Vs) tomograms which show a clear image of PSP and PAP. A depth to the top of PSP, 20 to 30 kilometer beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo

  9. Physical Model Method for Seismic Study of Concrete Dams

    Directory of Open Access Journals (Sweden)

    Bogdan Roşca

    2008-01-01

    Full Text Available The study of the dynamic behaviour of concrete dams by means of the physical model method is very useful to understand the failure mechanism of these structures to action of the strong earthquakes. Physical model method consists in two main processes. Firstly, a study model must be designed by a physical modeling process using the dynamic modeling theory. The result is a equations system of dimensioning the physical model. After the construction and instrumentation of the scale physical model a structural analysis based on experimental means is performed. The experimental results are gathered and are available to be analysed. Depending on the aim of the research may be designed an elastic or a failure physical model. The requirements for the elastic model construction are easier to accomplish in contrast with those required for a failure model, but the obtained results provide narrow information. In order to study the behaviour of concrete dams to strong seismic action is required the employment of failure physical models able to simulate accurately the possible opening of joint, sliding between concrete blocks and the cracking of concrete. The design relations for both elastic and failure physical models are based on dimensional analysis and consist of similitude relations among the physical quantities involved in the phenomenon. The using of physical models of great or medium dimensions as well as its instrumentation creates great advantages, but this operation involves a large amount of financial, logistic and time resources.

  10. Real-time detection and characterization of nuclear explosion using broadband analyses of regional seismic stations

    Science.gov (United States)

    Prastowo, T.; Madlazim

    2018-01-01

    This preliminary study aims to propose a new method of real-time detection and characterization of nuclear explosions by analyzing broadband seismic waveforms acquired from a network of regional seismic stations. Signal identification generated by a nuclear test was differentiated from natural sources of either earthquakes or other natural seismo-tectonic events by verifying crucial parameters, namely source depth, type of first motion, and P-wave domination of the broadband seismic wavesunder consideration. We examined and analyzed a recently hypothetical nuclear test performed by the North Koreangovernment that occurred on September 3, 2017 as a vital point to study. From spectral analyses, we found that the source of corresponding signals associated with detonations of the latest underground nuclear test was at a much shallower depth below the surface relatively compared with that of natural earthquakes, the suspected nuclear explosions produced compressional waves with radially directed outward from the source for their first motions, and the waves were only dominated by P-components. The results are then discussed in the context of potential uses of the proposed methodology for human-induced disaster early warning system and/or the need of rapid response purposes for minimizing the disaster risks.

  11. Coupling a Basin Modeling and a Seismic Code using MOAB

    KAUST Repository

    Yan, Mi; Jordan, Kirk; Kaushik, Dinesh; Perrone, Michael; Sachdeva, Vipin; Tautges, Timothy J.; Magerlein, John

    2012-01-01

    We report on a demonstration of loose multiphysics coupling between a basin modeling code and a seismic code running on a large parallel machine. Multiphysics coupling, which is one critical capability for a high performance computing (HPC) framework, was implemented using the MOAB open-source mesh and field database. MOAB provides for code coupling by storing mesh data and input and output field data for the coupled analysis codes and interpolating the field values between different meshes used by the coupled codes. We found it straightforward to use MOAB to couple the PBSM basin modeling code and the FWI3D seismic code on an IBM Blue Gene/P system. We describe how the coupling was implemented and present benchmarking results for up to 8 racks of Blue Gene/P with 8192 nodes and MPI processes. The coupling code is fast compared to the analysis codes and it scales well up to at least 8192 nodes, indicating that a mesh and field database is an efficient way to implement loose multiphysics coupling for large parallel machines.

  12. Coupling a Basin Modeling and a Seismic Code using MOAB

    KAUST Repository

    Yan, Mi

    2012-06-02

    We report on a demonstration of loose multiphysics coupling between a basin modeling code and a seismic code running on a large parallel machine. Multiphysics coupling, which is one critical capability for a high performance computing (HPC) framework, was implemented using the MOAB open-source mesh and field database. MOAB provides for code coupling by storing mesh data and input and output field data for the coupled analysis codes and interpolating the field values between different meshes used by the coupled codes. We found it straightforward to use MOAB to couple the PBSM basin modeling code and the FWI3D seismic code on an IBM Blue Gene/P system. We describe how the coupling was implemented and present benchmarking results for up to 8 racks of Blue Gene/P with 8192 nodes and MPI processes. The coupling code is fast compared to the analysis codes and it scales well up to at least 8192 nodes, indicating that a mesh and field database is an efficient way to implement loose multiphysics coupling for large parallel machines.

  13. Seismic variability of subduction thrust faults: Insights from laboratory models

    Science.gov (United States)

    Corbi, F.; Funiciello, F.; Faccenna, C.; Ranalli, G.; Heuret, A.

    2011-06-01

    Laboratory models are realized to investigate the role of interface roughness, driving rate, and pressure on friction dynamics. The setup consists of a gelatin block driven at constant velocity over sand paper. The interface roughness is quantified in terms of amplitude and wavelength of protrusions, jointly expressed by a reference roughness parameter obtained by their product. Frictional behavior shows a systematic dependence on system parameters. Both stick slip and stable sliding occur, depending on driving rate and interface roughness. Stress drop and frequency of slip episodes vary directly and inversely, respectively, with the reference roughness parameter, reflecting the fundamental role for the amplitude of protrusions. An increase in pressure tends to favor stick slip. Static friction is a steeply decreasing function of the reference roughness parameter. The velocity strengthening/weakening parameter in the state- and rate-dependent dynamic friction law becomes negative for specific values of the reference roughness parameter which are intermediate with respect to the explored range. Despite the simplifications of the adopted setup, which does not address the problem of off-fault fracturing, a comparison of the experimental results with the depth distribution of seismic energy release along subduction thrust faults leads to the hypothesis that their behavior is primarily controlled by the depth- and time-dependent distribution of protrusions. A rough subduction fault at shallow depths, unable to produce significant seismicity because of low lithostatic pressure, evolves into a moderately rough, velocity-weakening fault at intermediate depths. The magnitude of events in this range is calibrated by the interplay between surface roughness and subduction rate. At larger depths, the roughness further decreases and stable sliding becomes gradually more predominant. Thus, although interplate seismicity is ultimately controlled by tectonic parameters (velocity of

  14. Linking the Lusi mud eruption dynamics with regional and global seismic activity: a statistical analysis.

    Science.gov (United States)

    Collignon, Marine; Hammer, Øyvind; Fallahi, Mohammad J.; Lupi, Matteo; Schmid, Daniel W.; Alwi, Husein; Hadi, Soffian; Mazzini, Adriano

    2017-04-01

    The 29th May 2006, gas water and mud breccia started to erupt at several localities along the Watukosek fault system in the Sidoarjo Regency in East Java Indonesia. The most prominent eruption site, named Lusi, is still active and the emitted material now covers a surface of nearly 7 km2, resulting in the displacement of 60.000 people (up to date). Due to its social and economic impacts, as well as its spectacular dimensions, the Lusi eruption still attracts the attention of international media and scientists. In the framework of the Lusi Lab project (ERC grant n° 308126), many efforts were made to develop a quasi-constant monitoring of the site and the regional areas. Several studies attempted to predict the flow rate evolution or ground deformation, resulting in either overestimating or underestimating the longevity of the eruption. Models have failed because Lusi is not a mud volcano but a sedimentary hosted hydrothermal system that became apparent after the M6.3 Yogyakarta earthquake. Another reason is because such models usually assume that the flow will decrease pacing the overpressure reduction during the deflation of the chamber. These models typically consider a closed system with a unique chamber that is not being recharged. Overall the flow rate has decreased over the past ten years, although it has been largely fluctuating with monthly periods of higher mud breccia discharge. Monitoring of the eruption has revealed that numerous anomalous events are temporally linked to punctual events such as earthquakes or volcanic eruptions. Nevertheless, the quantification of these events has never been investigated in details. In this study, we present a compilation of anomalous events observed at the Lusi site during the last 10 years. Using Monte Carlo simulations, we then statistically compare the displacement, recorded at different seismic stations around Lusi, with the regional and global earthquakes catalogue to test the probability that an earthquake

  15. Simple model for post seismic ionospheric disturbances above an earthquake epicentre and along connecting magnetic field lines

    Directory of Open Access Journals (Sweden)

    R. Marchand

    2008-12-01

    Full Text Available The detection of ionospheric disturbances associated with seismic activity is one of the main objectives of the DEMETER micro-satellite. Its scientific payload provides a comprehensive set of electron and ion measurements. The present work describes a simple model of post-seismic disturbances in the ionosphere above the epicentre. Following a major seism, the neutral atmosphere is assumed to be subject to an acoustic pulse propagating upward, to high altitudes. By coupling this perturbation to the two-dimensional ionospheric model SAMI2 it is then possible to calculate the variations in a number of plasma parameters in the plume region and along connecting magnetic field lines, for an event of representative magnitude. The feasibility of identifying the signature of seismic events from satellite observations is then assessed in view of representative DEMETER measurements and of their natural variability.

  16. KFUPM-KAUST Red Sea model: Digital viscoelastic depth model and synthetic seismic data set

    KAUST Repository

    Al-Shuhail, Abdullatif A.; Mousa, Wail A.; Alkhalifah, Tariq Ali

    2017-01-01

    The Red Sea is geologically interesting due to its unique structures and abundant mineral and petroleum resources, yet no digital geologic models or synthetic seismic data of the Red Sea are publicly available for testing algorithms to image and analyze the area's interesting features. This study compiles a 2D viscoelastic model of the Red Sea and calculates a corresponding multicomponent synthetic seismic data set. The models and data sets are made publicly available for download. We hope this effort will encourage interested researchers to test their processing algorithms on this data set and model and share their results publicly as well.

  17. KFUPM-KAUST Red Sea model: Digital viscoelastic depth model and synthetic seismic data set

    KAUST Repository

    Al-Shuhail, Abdullatif A.

    2017-06-01

    The Red Sea is geologically interesting due to its unique structures and abundant mineral and petroleum resources, yet no digital geologic models or synthetic seismic data of the Red Sea are publicly available for testing algorithms to image and analyze the area\\'s interesting features. This study compiles a 2D viscoelastic model of the Red Sea and calculates a corresponding multicomponent synthetic seismic data set. The models and data sets are made publicly available for download. We hope this effort will encourage interested researchers to test their processing algorithms on this data set and model and share their results publicly as well.

  18. Forecasting Italian seismicity through a spatio-temporal physical model: importance of considering time-dependency and reliability of the forecast

    Directory of Open Access Journals (Sweden)

    Amir Hakimhashemi

    2010-11-01

    Full Text Available We apply here a forecasting model to the Italian region for the spatio-temporal distribution of seismicity based on a smoothing Kernel function, Coulomb stress variations, and a rate-and-state friction law. We tested the feasibility of this approach, and analyzed the importance of introducing time-dependency in forecasting future events. The change in seismicity rate as a function of time was estimated by calculating the Coulomb stress change imparted by large earthquakes. We applied our approach to the region of Italy, and used all of the cataloged earthquakes that occurred up to 2006 to generate the reference seismicity rate. For calculation of the time-dependent seismicity rate changes, we estimated the rate-and-state stress transfer imparted by all of the ML≥4.0 earthquakes that occurred during 2007 and 2008. To validate the results, we first compared the reference seismicity rate with the distribution of ML≥1.8 earthquakes since 2007, using both a non-declustered and a declustered catalog. A positive correlation was found, and all of the forecast earthquakes had locations within 82% and 87% of the study area with the highest seismicity rate, respectively. Furthermore, 95% of the forecast earthquakes had locations within 27% and 47% of the study area with the highest seismicity rate, respectively. For the time-dependent seismicity rate changes, the number of events with locations in the regions with a seismicity rate increase was 11% more than in the regions with a seismicity rate decrease.

  19. Mapping basin-wide subaquatic slope failure susceptibility as a tool to assess regional seismic and tsunami hazards

    Science.gov (United States)

    Strasser, Michael; Hilbe, Michael; Anselmetti, Flavio S.

    2010-05-01

    With increasing awareness of oceanic geohazards, submarine landslides are gaining wide attention because of their catastrophic impacts on both offshore infrastructures (e.g. pipelines, cables and platforms) and coastal areas (e.g. landslide-induced tsunamis). They also are of great interest because they can be directly related to primary trigger mechanisms including earthquakes, rapid sedimentation, gas release, glacial and tidal loading, wave action, or clathrate dissociation, many of which represent potential geohazards themselves. In active tectonic environments, for instance, subaquatic landslide deposits can be used to make inferences regarding the hazard derived from seismic activity. Enormous scientific and economic efforts are thus being undertaken to better determine and quantify causes and effects of natural hazards related to subaquatic landslides. In order to achieve this fundamental goal, the detailed study of past events, the assessment of their recurrence intervals and the quantitative reconstruction of magnitudes and intensities of both causal and subsequent processes and impacts are key requirements. Here we present data and results from a study using fjord-type Lake Lucerne in central Switzerland as a "model ocean" to test a new concept for the assessment of regional seismic and tsunami hazard by basin-wide mapping of critical slope stability conditions for subaquatic landslide initiation. Previously acquired high-resolution bathymetry and reflection seismic data as well as sedimentological and in situ geotechnical data, provide a comprehensive data base to investigate subaquatic landslides and related geohazards. Available data are implemented into a basin-wide slope model. In a Geographic Information System (GIS)-framework, a pseudo-static limit equilibrium infinite slope stability equation is solved for each model point representing reconstructed slope conditions at different times in the past, during which earthquake-triggered landslides

  20. Effects of induced stress on seismic forward modelling and inversion

    Science.gov (United States)

    Tromp, Jeroen; Trampert, Jeannot

    2018-05-01

    We demonstrate how effects of induced stress may be incorporated in seismic modelling and inversion. Our approach is motivated by the accommodation of pre-stress in global seismology. Induced stress modifies both the equation of motion and the constitutive relationship. The theory predicts that induced pressure linearly affects the unstressed isotropic moduli with a slope determined by their adiabatic pressure derivatives. The induced deviatoric stress produces anisotropic compressional and shear wave speeds; the latter result in shear wave splitting. For forward modelling purposes, we determine the weak form of the equation of motion under induced stress. In the context of the inverse problem, we determine induced stress sensitivity kernels, which may be used for adjoint tomography. The theory is illustrated by considering 2-D propagation of SH waves and related Fréchet derivatives based on a spectral-element method.

  1. The contribution of the Global Change Observatory Central Asia to seismic hazard and risk assessment in the Central Asian region

    Science.gov (United States)

    Parolai, S.; Bindi, D.; Haberland, C. A.; Pittore, M.; Pilz, M.; Rosenau, M.; Schurr, B.; Wieland, M.; Yuan, X.

    2012-12-01

    are necessary. Temporary seismic networks have been installed in several Central Asian cities (Bishkek and Karakol, Kyrgyzstan; Dushanbe, Tajikistan; Tashkent, Uzbekistan) within the framework of the Earthquake Model Central Asia (EMCA), a regional program of the Global Earthquake Model (GEM). The empirically estimated site effects have already helped to improve real-time risk scenarios for Bishkek and will be applied to other major cities. - A crucial requirement for disaster risk reduction involves the analysis of the vulnerability of existing building inventories. Whereas traditional approaches are very time- and cost-consuming, and even impossible given the high rate of urbanization in Central Asian capitals, our integrated approach is based on satellite remote sensing and ground-based omni-directional imaging, providing building inventories and thus structural vulnerability over large areas (EMCA, GEM-IDCT). All mentioned activities are carried out within the framework of cooperation between GFZ and regional national institutes, in particular the Central Asian Institute for Applied Geosciences. Altogether, this comprehensive and long-term risk analyses and research program will lead to a better understanding of the coupling of endogene and exogene processes and the identification of their impact on society.

  2. Development of a structural model for the nonlinear shear deformation behavior of a seismic isolator

    International Nuclear Information System (INIS)

    Lee, Jae Han; Koo, Gyeong Hoi; Yoo, Bong

    2002-02-01

    The seismic excitation test results of an isolated test structure for artificial time history excitation are summarized for structure models of the isolated structure and isolation bearing. To simulate the response characteristic of isolated structure, shear hysteresis curves of isolators are analyzed. A simple analysis model is developed representing the actual dynamic behaviors of the test model, and the seismic responses using the simple model of the isolated structure and structure models, which are developed such as linear and bilinear models for isolators, are performed and compared with those of the seismic tests. The developed bilinear model is well applicable only to large shear strain area of LLRB

  3. Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy seismic sequence

    Directory of Open Access Journals (Sweden)

    Silvia Pondrelli

    2012-10-01

    Full Text Available In May 2012, a seismic sequence struck the Emilia region (northern Italy. The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012 and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC, followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3 and the second at 11:00 UTC (Ml 5.2. For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M >5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.

  4. Theoretical models for crustal displacement assessment and monitoring in Vrancea-Focsani seismic zone by integrated remote sensing and local geophysical data for seismic prognosis

    International Nuclear Information System (INIS)

    Zoran, Maria; Ciobanu, Mircea; Mitrea, Marius Gabriel; Talianu, Camelia; Cotarlan, Costel; Mateciuc, Doru; Radulescu, Florin; Biter Mircea

    2002-01-01

    The majority of strong Romanian earthquakes has the origin in Vrancea region. Subduction of the Black Sea Sub-Plate under the Pannonian Plate produces faulting processes. Crustal displacement identification and monitoring is very important for a seismically active area like Vrancea-Focsani. Earthquake displacements are very well revealed by satellite remote sensing data. At the same time, geomorphologic analysis of topographic maps is carried out and particularly longitudinal and transverse profiles are constructed, as well as structural-geomorphologic maps. Faults are interpreted by specific features in nature of relief, straightness of line of river beds and their tributaries, exits of springs, etc. Remote sensing analysis and field studies of active faults can provide a geologic history that overcomes many of the shortcomings of instrumental and historic records. Our theoretical models developed in the frame of this project are presented as follows: a) Spectral Mixture Analysis model of geomorphological and topographic characteristics for Vrancea region proposed for satellite images analysis which assumes that the different classes present in a pixel (image unit) contribute independently to its reflectance. Therefore, the reflectance of a pixel at a particular frequency is the sum of the reflectances of the components at that frequency. The same test region in Vrancea area is imaged at several different frequencies (spectral bands), leading to multispectral observations for each pixel. It is useful to merge different satellite data into a hybrid image with high spatial and spectral resolution to create detailed images map of the abundance of various materials within the scene based on material spectral fingerprint. Image fusion produces a high-resolution multispectral image that is then unmixed into high-resolution material maps. b) Model of seismic cross section analysis which is applied in seismic active zones morphology. Since a seismic section can be

  5. Seismic structure of the western U.S. mantle and its relation to regional tectonic and magmatic activity

    Science.gov (United States)

    Schmandt, Brandon

    Vigorous convective activity in the western U.S. mantle has long been inferred from the region's widespread intra-plate crustal deformation, volcanism, and high elevations, but the specific form of convective activity and the degree and nature of lithospheric involvement have been strongly debated. I design a seismic travel-time tomography method and implement it with seismic data from the EarthScope Transportable Array and complementary arrays to constrain three-dimensional seismic structure beneath the western U.S. Tomographic images of variations in compressional velocity, shear velocity, and the ratio of shear to compressional velocity in the western U.S. mantle to a depth of 1000 km are produced. Using these results I investigate mantle physical properties, Cenozoic subduction history, and the influence of small-scale lithospheric convection on regional tectonic and magmatic activity, with particular focus on southern California and the Pacific Northwest. This dissertation includes previously published co-authored material. Chapter II presents a travel-time tomography method I designed and first implemented with data from southern California and the surrounding southwestern U.S. The resulting images provide a new level of constraint on upper mantle seismic anomalies beneath the Transverse Ranges, southern Great Valley, Salton Trough, and southwestern Nevada volcanic field. Chapter III presents tomographic images of the western U.S. mantle, identifies upper mantle volumes where partial melt is probable, and discusses implications of the apparently widespread occurrence of gravitational instabilities of continental lithsophere and the complex geometry and buoyancy of subducted ocean lithosphere imaged beneath the western U.S. In Chapter IV, tomography images are used in conjunction with geologic constraints on major transitions in crustal deformation and magmatism to construct a model for Pacific Northwest evolution since the Cretaceous. Accretion in the Pacific

  6. Joint innversion of seismic and magnetotelluric data in the Parkfield Region of California using the normalized cross-gradient constraint

    Science.gov (United States)

    Bennington, Ninfa L.; Zhang, Haijiang; Thurber, Cliff; Bedrosian, Paul A.

    2015-01-01

    We present jointly inverted models of P-wave velocity (Vp) and electrical resistivity for a two-dimensional profile centered on the San Andreas Fault Observatory at Depth (SAFOD). Significant structural similarity between main features of the separately inverted Vp and resistivity models is exploited by carrying out a joint inversion of the two datasets using the normalized cross-gradient constraint. This constraint favors structurally similar Vp and resistivity images that adequately fit the seismic and magnetotelluric (MT) datasets. The new inversion code, tomoDDMT, merges the seismic inversion code tomoDD and the forward modeling and sensitivity kernel subroutines of the MT inversion code OCCAM2DMT. TomoDDMT is tested on a synthetic dataset and demonstrates the code’s ability to more accurately resolve features of the input synthetic structure relative to the separately inverted resistivity and velocity models. Using tomoDDMT, we are able to resolve a number of key issues raised during drilling at SAFOD. We are able to infer the distribution of several geologic units including the Salinian granitoids, the Great Valley sequence, and the Franciscan Formation. The distribution and transport of fluids at both shallow and great depths is also examined. Low values of velocity/resistivity attributed to a feature known as the Eastern Conductor (EC) can be explained in two ways: the EC is a brine-filled, high porosity region, or this region is composed largely of clay-rich shales of the Franciscan. The Eastern Wall, which lies immediately adjacent to the EC, is unlikely to be a fluid pathway into the San Andreas Fault’s seismogenic zone due to its observed higher resistivity and velocity values.

  7. The Scandinavian regional model

    DEFF Research Database (Denmark)

    Torfing, Jacob; Lidström, Anders; Røiseland, Asbjørn

    2015-01-01

    This article maps how the sub-national regional levels of governance in Denmark, Norway and Sweden have changed from a high degree of institutional convergence to a pattern of institutional divergence. It analyses the similarities and differences in the changes in regional governance and discusses...

  8. The 2014 United States National Seismic Hazard Model

    Science.gov (United States)

    Petersen, Mark D.; Moschetti, Morgan P.; Powers, Peter; Mueller, Charles; Haller, Kathleen; Frankel, Arthur; Zeng, Yuehua; Rezaeian, Sanaz; Harmsen, Stephen; Boyd, Oliver; Field, Edward; Chen, Rui; Rukstales, Kenneth S.; Luco, Nicolas; Wheeler, Russell; Williams, Robert; Olsen, Anna H.

    2015-01-01

    New seismic hazard maps have been developed for the conterminous United States using the latest data, models, and methods available for assessing earthquake hazard. The hazard models incorporate new information on earthquake rupture behavior observed in recent earthquakes; fault studies that use both geologic and geodetic strain rate data; earthquake catalogs through 2012 that include new assessments of locations and magnitudes; earthquake adaptive smoothing models that more fully account for the spatial clustering of earthquakes; and 22 ground motion models, some of which consider more than double the shaking data applied previously. Alternative input models account for larger earthquakes, more complicated ruptures, and more varied ground shaking estimates than assumed in earlier models. The ground motions, for levels applied in building codes, differ from the previous version by less than ±10% over 60% of the country, but can differ by ±50% in localized areas. The models are incorporated in insurance rates, risk assessments, and as input into the U.S. building code provisions for earthquake ground shaking.

  9. Combined GPS and seismic monitoring of a 12-story structure in a region of induced seismicity in Oklahoma

    Science.gov (United States)

    Haase, J. S.; Soliman, M.; Kim, H.; Jaiswal, P.; Saunders, J. K.; Vernon, F.; Zhang, W.

    2017-12-01

    This work focuses on quantifying ground motions and their effects in Oklahoma near the location of the 2016 Mw 5.8 Pawnee earthquake, where seismicity has been increasing due to wastewater injection related to oil and natural gas production. Much of the building inventory in Oklahoma was constructed before the increase in seismicity and before the implementation of earthquake design and detailing provisions for reinforced concrete (RC) structures. We will use combined GPS/seismic monitoring techniques to measure ground motion in the field and the response of structures to this ground motion. Several Oklahoma State University buildings experienced damage due to the Pawnee earthquake. The USGS Shake Map product estimated peak ground acceleration (PGA) ranging from 0.12g to 0.15g at campus locations. We are deploying a high-rate GPS sensor and accelerometer on the roof and another accelerometer at ground level of a 12-story RC structure and at selected field sites in order to collect ambient noise data and nearby seismicity. The longer period recording characteristics of the GPS/seismic system are particularly well adapted to monitoring these large structures in the event of a significant earthquake. Gross characteristics of the structural system are described, which consists of RC columns and RC slabs in all stories. We conducted a preliminary structural analysis including modal analysis and response spectrum analysis based on a finite element (FE) simulation, which indicated that the period associated with the first X-axis bending, first torsional, and first Y-axis bending modes are 2.2 s, 2.1 s, and 1.8 s, respectively. Next, a preliminary analysis was conducted to estimate the range of expected deformation at the roof level for various earthquake excitations. The earthquake analysis shows a maximum roof displacement of 5 and 7 cm in the horizontal directions resulting from earthquake loads with PGA of 0.2g, well above the noise level of the combined GPS/seismic

  10. Crustal Models Assessment in Western Part of Romania Employing Active Seismic and Seismologic Methods

    Science.gov (United States)

    Bala, Andrei; Toma-Danila, Dragos; Tataru, Dragos; Grecu, Bogdan

    2017-12-01

    In the years 1999 - 2000 two regional seismic refraction lines were performed within a close cooperation with German partners from University of Karlsruhe. One of these lines is Vrancea 2001, with 420 km in length, almost half of them recorded in Transylvanian Basin. The structure of the crust along the seismic line revealed a very complicated crustal structure beginning with Eastern Carpathians and continuing in the Transylvanian Basin until Medias. As a result of the development of the National Seismic Network in the last ten years, more than 100 permanent broadband stations are now continuously operating in Romania. Complementary to this national dataset, maintained and developed in the National Institute for Earth Physics, new data emerged from the temporary seismologic networks established during the joint projects with European partners in the last decades. The data gathered so far is valuable both for seismology purposes and crustal structure studies, especially for the western part of the country, where this kind of data were sparse until now. Between 2009 and 2011, a new reference model for the Earth’s crust and mantle of the European Plate was defined through the NERIES project from existing data and models. The database gathered from different kind of measurements in Transylvanian Basin and eastern Pannonian Basin were included in this NERIES model and an improved and upgraded model of the Earth crust emerged for western part of Romania. Although the dataset has its origins in several periods over the last 50 years, the results are homogeneous and they improve and strengthen our image about the depth of the principal boundaries in the crust. In the last chapter two maps regarding these boundaries are constructed, one for mid-crustal boundary and one for Moho. They were build considering all the punctual information available from different sources in active seismic and seismology which are introduced in the general maps from the NERIES project for

  11. Numerical modeling and experimental validation of seismic uplift pressure variations in cracked concrete dams

    Energy Technology Data Exchange (ETDEWEB)

    Javanmardi, F.; Leger, P. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Civil, Mining and Geological Engineering; Tinawi, R. [Quebec Univ., Montreal, PQ (Canada)

    2004-07-01

    Concrete dams could sustain cracking and damage during maximum design earthquakes (MDE). Dam safety guidelines are established so that dams maintain a stable condition following MDE oscillatory motions. In this study, a theoretical model was developed to calculate the uplift pressure variations along concrete cracks with moving walls. The proposed model was verified using experimental crack test data. The model was applied in a finite element computer program for dynamic analysis of gravity dams considering hydro-mechanical water-crack coupling. An analysis of a typical 90 metre dam subjected to low and high frequency sinusoidal accelerations demonstrated that water can penetrate into part of a seismically initiated crack. Pressure tends to develop in a region close to the crack mouth, therefore detrimental effects for the global dam stability are unlikely to occur. The study showed that the seismic uplift force during the heel crack opening mode is small compared to the dam weight. This preliminary study suggests that the critical sliding safety factors (SSF) of the dam against downstream sliding could be computed by considering zero uplift pressure in the crack region subjected to tensile opening. 14 refs., 1 tab., 7 figs.

  12. Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

    Science.gov (United States)

    Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

    2016-11-01

    A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

  13. Mechanical tests for validation of seismic isolation elastomer constitutive models

    International Nuclear Information System (INIS)

    Kulak, R.F.; Hughes, T.H.

    1992-01-01

    High damping laminated elastomeric bearings are becoming the preferred device for seismic isolation of large buildings and structures, such as nuclear power plants. The key component of these bearings is a filled natural rubber elastomer. This material exhibits nonlinear behavior within the normal design range. The material damping cannot be classified as either viscous or hysteritic, but it seems to fall somewhere in between. This paper describes a series of tests that can be used to characterize the mechanical response of these elastomers. The tests are designed to determine the behavior of the elastomer in the time scale of the earthquake, which is typically from 30 to 60 seconds. The test results provide data for use in determining the material parameters associated with nonlinear constitutive models. 4 refs

  14. Preliminary deformation model for National Seismic Hazard map of Indonesia

    Energy Technology Data Exchange (ETDEWEB)

    Meilano, Irwan; Gunawan, Endra; Sarsito, Dina; Prijatna, Kosasih; Abidin, Hasanuddin Z. [Geodesy Research Division, Faculty of Earth Science and Technology, Institute of Technology Bandung (Indonesia); Susilo,; Efendi, Joni [Agency for Geospatial Information (BIG) (Indonesia)

    2015-04-24

    Preliminary deformation model for the Indonesia’s National Seismic Hazard (NSH) map is constructed as the block rotation and strain accumulation function at the elastic half-space. Deformation due to rigid body motion is estimated by rotating six tectonic blocks in Indonesia. The interseismic deformation due to subduction is estimated by assuming coupling on subduction interface while deformation at active fault is calculated by assuming each of the fault‘s segment slips beneath a locking depth or in combination with creeping in a shallower part. This research shows that rigid body motion dominates the deformation pattern with magnitude more than 15 mm/year, except in the narrow area near subduction zones and active faults where significant deformation reach to 25 mm/year.

  15. Mathematical model of the seismic electromagnetic signals (SEMS) in non crystalline substances

    Energy Technology Data Exchange (ETDEWEB)

    Dennis, L. C. C.; Yahya, N.; Daud, H.; Shafie, A. [Electromagnetic cluster, Universiti Teknologi Petronas, 31750 Tronoh, Perak (Malaysia)

    2012-09-26

    The mathematical model of seismic electromagnetic waves in non crystalline substances is developed and the solutions are discussed to show the possibility of improving the electromagnetic waves especially the electric field. The shear stress of the medium in fourth order tensor gives the equation of motion. Analytic methods are selected for the solutions written in Hansen vector form. From the simulated SEMS, the frequency of seismic waves has significant effects to the SEMS propagating characteristics. EM waves transform into SEMS or energized seismic waves. Traveling distance increases once the frequency of the seismic waves increases from 100% to 1000%. SEMS with greater seismic frequency will give seismic alike waves but greater energy is embedded by EM waves and hence further distance the waves travel.

  16. Mathematical model of the seismic electromagnetic signals (SEMS) in non crystalline substances

    International Nuclear Information System (INIS)

    Dennis, L. C. C.; Yahya, N.; Daud, H.; Shafie, A.

    2012-01-01

    The mathematical model of seismic electromagnetic waves in non crystalline substances is developed and the solutions are discussed to show the possibility of improving the electromagnetic waves especially the electric field. The shear stress of the medium in fourth order tensor gives the equation of motion. Analytic methods are selected for the solutions written in Hansen vector form. From the simulated SEMS, the frequency of seismic waves has significant effects to the SEMS propagating characteristics. EM waves transform into SEMS or energized seismic waves. Traveling distance increases once the frequency of the seismic waves increases from 100% to 1000%. SEMS with greater seismic frequency will give seismic alike waves but greater energy is embedded by EM waves and hence further distance the waves travel.

  17. Crustal evolution of Eocene paleo arc around Ogasawara region obtained by seismic reflection survey

    Science.gov (United States)

    Yamashita, M.; Takahashi, N.; Kodaira, S.; Miura, S.; Ishizuka, O.; Tatsumi, Y.

    2011-12-01

    The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. The existence of two paleo arc which consists of Oligocene and Eocene paleo age is known in IBM forearc region by geological and geophysical studies. The Ogasawara ridge is also known to locate the initial structure of arc evolution from geologic sampling of research submersible. In this region, IODP drilling site: IBM-2 is proposed in order to understand the temporal and spatial change in arc crust composition from 50 to 40Ma magmatism. Site IBM-2 consists of two offset drilling holes (BON-1, BON-2). BON-1 designed to first encounter forearc basalt and will reach the sheeted dykes. BON-2 will start in boninites and finish in fore arc basalts. The purpose of these drilling is sampling the full volcanic stratigraphy from gabbro to boninite. There is no seismic data around BON-1 and BON-2, therefore it is need to conduct the multi-channel seismic reflection survey. Japan Agency for Marine-Earth Science and Technology carried out multi-channel seismic reflection survey and wide-angle reflection survey using 7,800 cu.in. air gun, 5 km streamer with 444 ch hydrophones and 40 OBSs in March 2011. We obtained two seismic reflection profiles of lines KT06 and KT07 along the paleo arc around Ogasawara ridge. Line KT06 located the north side of Ogasawara ridge. Line KT07 located the trench side of Ogasawara ridge. Lines KT06 is also deployed the OBSs every 5 km interval. Thin sediments are covered with basement in both survey lines. There are some sediment filled in depression topography. The low-frequency reflection from the top of subducting Pacific plate is recognized in line KT06. The continuity of this reflection is not clear due to the complicated bathymetry. The displacement of basement in northern side of Ogasawara ridge is identified along the lineament of bathymetry in Line 06. This structure is

  18. A global database of seismically and non-seismically triggered landslides for 2D/3D numerical modeling

    Science.gov (United States)

    Domej, Gisela; Bourdeau, Céline; Lenti, Luca; Pluta, Kacper

    2017-04-01

    Landsliding is a worldwide common phenomenon. Every year, and ranging in size from very small to enormous, landslides cause all too often loss of life and disastrous damage to infrastructure, property and the environment. One main reason for more frequent catastrophes is the growth of population on the Earth which entails extending urbanization to areas at risk. Landslides are triggered by a variety and combination of causes, among which the role of water and seismic activity appear to have the most serious consequences. In this regard, seismic shaking is of particular interest since topographic elevation as well as the landslide mass itself can trap waves and hence amplify incoming surface waves - a phenomenon known as "site effects". Research on the topic of landsliding due to seismic and non-seismic activity is extensive and a broad spectrum of methods for modeling slope deformation is available. Those methods range from pseudo-static and rigid-block based models to numerical models. The majority is limited to 2D modeling since more sophisticated approaches in 3D are still under development or calibration. However, the effect of lateral confinement as well as the mechanical properties of the adjacent bedrock might be of great importance because they may enhance the focusing of trapped waves in the landslide mass. A database was created to study 3D landslide geometries. It currently contains 277 distinct seismically and non-seismically triggered landslides spread all around the globe whose rupture bodies were measured in all available details. Therefore a specific methodology was developed to maintain predefined standards, to keep the bias as low as possible and to set up a query tool to explore the database. Besides geometry, additional information such as location, date, triggering factors, material, sliding mechanisms, event chronology, consequences, related literature, among other things are stored for every case. The aim of the database is to enable

  19. Moho Depth and Geometry in the Illinois Basin Region Based on Gravity and Seismic Data from an EarthScope FlexArray Experiment

    Science.gov (United States)

    Curcio, D. D.; Pavlis, G. L.; Yang, X.; Hamburger, M. W.; Zhang, H.; Ravat, D.

    2017-12-01

    We present results from a combined analysis of seismic and gravity in the Illinois Basin region that demonstrate the presence of an unusually deep and highly variable Moho discontinuity. We construct a new, high-resolution image of the Earth's crust beneath the Illinois Basin using teleseismic P-wave receiver functions from the EarthScope OIINK (Ozarks, Illinois, INdiana, Kentucky) Flexible Array and the USArray Transportable Array. Our seismic analyses involved data from 143 OIINK stations and 80 USArray stations, using 3D plane-wave migration and common conversion point (CCP) stacking of P-to-S conversion data. Seismic interpretation has been done using the seismic exploration software package Petrel. One of the most surprising results is the anomalous depth of the Moho in this area, ranging from 41 to 63 km, with an average depth of 50 km. This thickened crust is unexpected in the Illinois Basin area, which has not been subject to convergence and mountain building processes in the last 900 Ma. This anomalously thick crust in combination with the minimal topography requires abnormally dense lower crust or unusually light upper mantle in order to retain gravitational equilibrium. Combining gravity modeling with the seismically identified Moho and a ubiquitous lower crustal boundary, we solve for the density variation of the middle and lower crust. We test the hypothesis that the anomalously thick crust and its high lower crustal layer observed in most of the central and southeastern Illinois Basin predates the formation and development of the current Illinois Basin. Post-formation tectonic activity, such as late Precambrian rifting or underplating are inferred to have modified the crustal thickness as well. The combination of high-resolution seismic data analysis and gravity modeling promises to provide additional insight into the geometry and composition of the lower crust in the Illinois Basin area.

  20. Irregularities in Early Seismic Rupture Propagation for Large Events in a Crustal Earthquake Model

    Science.gov (United States)

    Lapusta, N.; Rice, J. R.; Rice, J. R.

    2001-12-01

    We study early seismic propagation of model earthquakes in a 2-D model of a vertical strike-slip fault with depth-variable rate and state friction properties. Our model earthquakes are obtained in fully dynamic simulations of sequences of instabilities on a fault subjected to realistically slow tectonic loading (Lapusta et al., JGR, 2000). This work is motivated by results of Ellsworth and Beroza (Science, 1995), who observe that for many earthquakes, far-field velocity seismograms during initial stages of dynamic rupture propagation have irregular fluctuations which constitute a "seismic nucleation phase". In our simulations, we find that such irregularities in velocity seismograms can be caused by two factors: (1) rupture propagation over regions of stress concentrations and (2) partial arrest of rupture in neighboring creeping regions. As rupture approaches a region of stress concentration, it sees increasing background stress and its moment acceleration (to which velocity seismographs in the far field are proportional) increases. After the peak in stress concentration, the rupture sees decreasing background stress and moment acceleration decreases. Hence a fluctuation in moment acceleration is created. If rupture starts sufficiently far from a creeping region, then partial arrest of rupture in the creeping region causes a decrease in moment acceleration. As the other parts of rupture continue to develop, moment acceleration then starts to grow again, and a fluctuation again results. Other factors may cause the irregularities in moment acceleration, e.g., phenomena such as branching and/or intermittent rupture propagation (Poliakov et al., submitted to JGR, 2001) which we have not studied here. Regions of stress concentration are created in our model by arrest of previous smaller events as well as by interactions with creeping regions. One such region is deep in the fault zone, and is caused by the temperature-induced transition from seismogenic to creeping

  1. Forecasting Induced Seismicity Using Saltwater Disposal Data and a Hydromechanical Earthquake Nucleation Model

    Science.gov (United States)

    Norbeck, J. H.; Rubinstein, J. L.

    2017-12-01

    The earthquake activity in Oklahoma and Kansas that began in 2008 reflects the most widespread instance of induced seismicity observed to date. In this work, we demonstrate that the basement fault stressing conditions that drive seismicity rate evolution are related directly to the operational history of 958 saltwater disposal wells completed in the Arbuckle aquifer. We developed a fluid pressurization model based on the assumption that pressure changes are dominated by reservoir compressibility effects. Using injection well data, we established a detailed description of the temporal and spatial variability in stressing conditions over the 21.5-year period from January 1995 through June 2017. With this stressing history, we applied a numerical model based on rate-and-state friction theory to generate seismicity rate forecasts across a broad range of spatial scales. The model replicated the onset of seismicity, the timing of the peak seismicity rate, and the reduction in seismicity following decreased disposal activity. The behavior of the induced earthquake sequence was consistent with the prediction from rate-and-state theory that the system evolves toward a steady seismicity rate depending on the ratio between the current and background stressing rates. Seismicity rate transients occurred over characteristic timescales inversely proportional to stressing rate. We found that our hydromechanical earthquake rate model outperformed observational and empirical forecast models for one-year forecast durations over the period 2008 through 2016.

  2. Seismic Modeling Of Reservoir Heterogeneity Scales: An Application To Gas Hydrate Reservoirs

    Science.gov (United States)

    Huang, J.; Bellefleur, G.; Milkereit, B.

    2008-12-01

    Natural gas hydrates, a type of inclusion compound or clathrate, are composed of gas molecules trapped within a cage of water molecules. The occurrence of gas hydrates in permafrost regions has been confirmed by core samples recovered from the Mallik gas hydrate research wells located within Mackenzie Delta in Northwest Territories of Canada. Strong vertical variations of compressional and shear sonic velocities and weak surface seismic expressions of gas hydrates indicate that lithological heterogeneities control the distribution of hydrates. Seismic scattering studies predict that typical scales and strong physical contrasts due to gas hydrate concentration will generate strong forward scattering, leaving only weak energy captured by surface receivers. In order to understand the distribution of hydrates and the seismic scattering effects, an algorithm was developed to construct heterogeneous petrophysical reservoir models. The algorithm was based on well logs showing power law features and Gaussian or Non-Gaussian probability density distribution, and was designed to honor the whole statistical features of well logs such as the characteristic scales and the correlation among rock parameters. Multi-dimensional and multi-variable heterogeneous models representing the same statistical properties were constructed and applied to the heterogeneity analysis of gas hydrate reservoirs. The petrophysical models provide the platform to estimate rock physics properties as well as to study the impact of seismic scattering, wave mode conversion, and their integration on wave behavior in heterogeneous reservoirs. Using the Biot-Gassmann theory, the statistical parameters obtained from Mallik 5L-38, and the correlation length estimated from acoustic impedance inversion, gas hydrate volume fraction in Mallik area was estimated to be 1.8%, approximately 2x108 m3 natural gas stored in a hydrate bearing interval within 0.25 km2 lateral extension and between 889 m and 1115 m depth

  3. The 2018 and 2020 Updates of the U.S. National Seismic Hazard Models

    Science.gov (United States)

    Petersen, M. D.

    2017-12-01

    During 2018 the USGS will update the 2014 National Seismic Hazard Models by incorporating new seismicity models, ground motion models, site factors, fault inputs, and by improving weights to ground motion models using empirical and other data. We will update the earthquake catalog for the U.S. and introduce new rate models. Additional fault data will be used to improve rate estimates on active faults. New ground motion models (GMMs) and site factors for Vs30 have been released by the Pacific Earthquake Engineering Research Center (PEER) and we will consider these in assessing ground motions in craton and extended margin regions of the central and eastern U.S. The USGS will also include basin-depth terms for selected urban areas of the western United States to improve long-period shaking assessments using published depth estimates to 1.0 and 2.5 km/s shear wave velocities. We will produce hazard maps for input into the building codes that span a broad range of periods (0.1 to 5 s) and site classes (shear wave velocity from 2000 m/s to 200 m/s in the upper 30 m of the crust, Vs30). In the 2020 update we plan on including: a new national crustal model that defines basin depths required in the latest GMMs, new 3-D ground motion simulations for several urban areas, new magnitude-area equations, and new fault geodetic and geologic strain rate models. The USGS will also consider including new 3-D ground motion simulations for inclusion in these long-period maps. These new models are being evaluated and will be discussed at one or more regional and topical workshops held at the beginning of 2018.

  4. Reservoir creep and induced seismicity: inferences from geomechanical modeling of gas depletion in the Groningen field

    Science.gov (United States)

    van Wees, Jan-Diederik; Osinga, Sander; Van Thienen-Visser, Karin; Fokker, Peter A.

    2018-03-01

    The Groningen gas field in the Netherlands experienced an immediate reduction in seismic events in the year following a massive cut in production. This reduction is inconsistent with existing models of seismicity predictions adopting compaction strains as proxy, since reservoir creep would then result in a more gradual reduction of seismic events after a production stop. We argue that the discontinuity in seismic response relates to a physical discontinuity in stress loading rate on faults upon the arrest of pressure change. The stresses originate from a combination of the direct poroelastic effect through the pressure changes and the delayed effect of ongoing compaction after cessation of reservoir production. Both mechanisms need to be taken into account. To this end, we employed finite-element models in a workflow that couples Kelvin-Chain reservoir creep with a semi-analytical approach for the solution of slip and seismic moment from the predicted stress change. For ratios of final creep and elastic compaction up to 5, the model predicts that the cumulative seismic moment evolution after a production stop is subject to a very moderate increase, 2-10 times less than the values predicted by the alternative approaches using reservoir compaction strain as proxy. This is in agreement with the low seismicity in the central area of the Groningen field immediately after reduction in production. The geomechanical model findings support scope for mitigating induced seismicity through adjusting rates of pressure change by cutting down production.

  5. An experimental investigation for scalability of the seismic response of microconcrete model nuclear power plant structures

    International Nuclear Information System (INIS)

    Bennett, J.G.; Dove, R.C.; Dunwoody, W.E.; Farrar, C.R.

    1987-01-01

    The paper reports the results from tests including reduced stiffnesses found in the prototype and 1/4 scale model, implications of the test results on the validity of past tests, and implications of these results from the 1986 tests on the seismic behavior of actual Seismic Category I Structures and their attached equipment. (orig./HP)

  6. Global seasonal strain and stress models derived from GRACE loading, and their impact on seismicity

    Science.gov (United States)

    Chanard, K.; Fleitout, L.; Calais, E.; Craig, T. J.; Rebischung, P.; Avouac, J. P.

    2017-12-01

    Loading by continental water, atmosphere and oceans deforms the Earth at various spatio-temporal scales, inducing crustal and mantelic stress perturbations that may play a role in earthquake triggering.Deformation of the Earth by this surface loading is observed in GNSS position time series. While various models predict well vertical observations, explaining horizontal displacements remains challenging. We model the elastic deformation induced by loading derived from GRACE for coefficients 2 and higher. We estimate the degree-1 deformation field by comparison between predictions of our model and IGS-repro2 solutions at a globally distributed network of 700 GNSS sites, separating the horizontal and vertical components to avoid biases between components. The misfit between model and data is reduced compared to previous studies, particularly on the horizontal component. The associated geocenter motion time series are consistent with results derived from other datasets. We also discuss the impact on our results of systematic errors in GNSS geodetic products, in particular of the draconitic error.We then compute stress tensors time series induced by GRACE loads and discuss the potential link between large scale seasonal mass redistributions and seismicity. Within the crust, we estimate hydrologically induced stresses in the intraplate New Madrid Seismic Zone, where secular stressing rates are unmeasurably low. We show that a significant variation in the rate of micro-earthquakes at annual and multi-annual timescales coincides with stresses induced by hydrological loading in the upper Mississippi embayment, with no significant phase-lag, directly modulating regional seismicity. We also investigate pressure variations in the mantle transition zone and discuss potential correlations between the statistically significant observed seasonality of deep-focus earthquakes, most likely due to mineralogical transformations, and surface hydrological loading.

  7. Development of a State-Wide 3-D Seismic Tomography Velocity Model for California

    Science.gov (United States)

    Thurber, C. H.; Lin, G.; Zhang, H.; Hauksson, E.; Shearer, P.; Waldhauser, F.; Hardebeck, J.; Brocher, T.

    2007-12-01

    We report on progress towards the development of a state-wide tomographic model of the P-wave velocity for the crust and uppermost mantle of California. The dataset combines first arrival times from earthquakes and quarry blasts recorded on regional network stations and travel times of first arrivals from explosions and airguns recorded on profile receivers and network stations. The principal active-source datasets are Geysers-San Pablo Bay, Imperial Valley, Livermore, W. Mojave, Gilroy-Coyote Lake, Shasta region, Great Valley, Morro Bay, Mono Craters-Long Valley, PACE, S. Sierras, LARSE 1 and 2, Loma Prieta, BASIX, San Francisco Peninsula and Parkfield. Our beta-version model is coarse (uniform 30 km horizontal and variable vertical gridding) but is able to image the principal features in previous separate regional models for northern and southern California, such as the high-velocity subducting Gorda Plate, upper to middle crustal velocity highs beneath the Sierra Nevada and much of the Coast Ranges, the deep low-velocity basins of the Great Valley, Ventura, and Los Angeles, and a high- velocity body in the lower crust underlying the Great Valley. The new state-wide model has improved areal coverage compared to the previous models, and extends to greater depth due to the data at large epicentral distances. We plan a series of steps to improve the model. We are enlarging and calibrating the active-source dataset as we obtain additional picks from investigators and perform quality control analyses on the existing and new picks. We will also be adding data from more quarry blasts, mainly in northern California, following an identification and calibration procedure similar to Lin et al. (2006). Composite event construction (Lin et al., in press) will be carried out for northern California for use in conventional tomography. A major contribution of the state-wide model is the identification of earthquakes yielding arrival times at both the Northern California Seismic

  8. Seismic wavefield modeling based on time-domain symplectic and Fourier finite-difference method

    Science.gov (United States)

    Fang, Gang; Ba, Jing; Liu, Xin-xin; Zhu, Kun; Liu, Guo-Chang

    2017-06-01

    Seismic wavefield modeling is important for improving seismic data processing and interpretation. Calculations of wavefield propagation are sometimes not stable when forward modeling of seismic wave uses large time steps for long times. Based on the Hamiltonian expression of the acoustic wave equation, we propose a structure-preserving method for seismic wavefield modeling by applying the symplectic finite-difference method on time grids and the Fourier finite-difference method on space grids to solve the acoustic wave equation. The proposed method is called the symplectic Fourier finite-difference (symplectic FFD) method, and offers high computational accuracy and improves the computational stability. Using acoustic approximation, we extend the method to anisotropic media. We discuss the calculations in the symplectic FFD method for seismic wavefield modeling of isotropic and anisotropic media, and use the BP salt model and BP TTI model to test the proposed method. The numerical examples suggest that the proposed method can be used in seismic modeling of strongly variable velocities, offering high computational accuracy and low numerical dispersion. The symplectic FFD method overcomes the residual qSV wave of seismic modeling in anisotropic media and maintains the stability of the wavefield propagation for large time steps.

  9. LANDSAT TM and SAR - ERS1 data for analysis of Vrancea seismic region

    International Nuclear Information System (INIS)

    Zoran, M.

    2002-01-01

    This paper is aimed to present the results of the application of LANDSAT TM and SAR- ERS1 satellite data for Vrancea seismic area investigation, in order to emphasize geomorphological features as well as to identify faulting zones responsible of seismic events generation. Remote sensing analysis and field studies of active faults can provide a geologic history that overcomes many of the shortcomings of instrumental and historic records. Vrancea - Focsani is structurally and seismically complex area, bounded by latitudes 45.6 angle N and 46.0 angle N and longitudes 26.5 angle E and 27.5 angle E. The Peceneaga -Camena Fault, a deep crustal fracture with dextral slip, is considered to be North-Eastern boundary of the Moesian Platform. The Eastern unit of the Moesian Sub-Plate is characterized by a series of principal faults with a North-Western orientation and by a secondary system of faults orientated NE-SW. NW trending crustal fractures are also evidenced East of the Peceneaga-Camena Fault, within our test area. A SAR- ERS1 image and a multispectral Landsat TM data set were used and processed with EASI/PACE image processing software package as well as with developed algorithms. In order to a better management all the information available on the study area, data acquired have been integrated in a unique database. This information consists of thematic maps from cartography, land use map from classification of remotely sensed data. This study revealed that satellite data used are excellent for recognizing the continuity and regional relationships of faults. Linear features in TM images appear shorter and denser distributed, whereas ERS1 images are dominated by the principal structures. In certain cases they complete the lineaments and lineament patterns derived from TM data. Higher spatial resolution satellite data and SAR interferometric data are needed for mapping of these features. Remote sensing techniques provide a means for locating, identifying and mapping

  10. Development of a seismic source model for probabilistic seismic hazard assessment of nuclear power plant sites in Switzerland: the view from PEGASOS Expert Group 4 (EG1d)

    International Nuclear Information System (INIS)

    Wiemer, S.; Garcia-Fernandez, M.; Burg, J.-P.

    2009-01-01

    We present a seismogenic source model for site-specific probabilistic seismic hazard assessment at the sites of Swiss nuclear power plants. Our model is one of four developed in the framework of the PEGASOS project; it contains a logic tree with nine levels of decision-making. The two primary sources of input used in the areal zonation developed by us are the historical and instrumental seismicity record and large-scale geological/rheological units. From this, we develop a zonation of six macro zones, refined in a series of seven decision steps up to a maximum of 13 zones. Within zones, activity rates are either assumed homogeneous or smoothed using a Gaussian kernel with width of 5 or 15 km. To estimate recurrence rate, we assume a double truncated Gutenberg-Richter law, and consider five models of recurrence parameters with different degrees of freedom. Models are weighted in the logic tree using a weighted Akaike score. The maximum magnitude is estimated following the EPRI approach. We perform extensive sensitivity analyses in rate and hazard space in order to assess the role of de-clustering, the completeness model, quarry contamination, border properties, stationarity, regional b-value and magnitude-dependent hypocentral depth. (author)

  11. Development of a seismic source model for probabilistic seismic hazard assessment of nuclear power plant sites in Switzerland: the view from PEGASOS Expert Group 4 (EG1d)

    Energy Technology Data Exchange (ETDEWEB)

    Wiemer, S. [Institute of Geophysics, ETH Zuerich, Zuerich (Switzerland); Garcia-Fernandez, M. [Spanish Council for Scientific Research, Museum of Natural History, Dept. of Volcanology and Geophysics, Madrid (Spain); Burg, J.-P. [Institute of Geology, ETH Zuerich, Zuerich (Switzerland)

    2009-05-15

    We present a seismogenic source model for site-specific probabilistic seismic hazard assessment at the sites of Swiss nuclear power plants. Our model is one of four developed in the framework of the PEGASOS project; it contains a logic tree with nine levels of decision-making. The two primary sources of input used in the areal zonation developed by us are the historical and instrumental seismicity record and large-scale geological/rheological units. From this, we develop a zonation of six macro zones, refined in a series of seven decision steps up to a maximum of 13 zones. Within zones, activity rates are either assumed homogeneous or smoothed using a Gaussian kernel with width of 5 or 15 km. To estimate recurrence rate, we assume a double truncated Gutenberg-Richter law, and consider five models of recurrence parameters with different degrees of freedom. Models are weighted in the logic tree using a weighted Akaike score. The maximum magnitude is estimated following the EPRI approach. We perform extensive sensitivity analyses in rate and hazard space in order to assess the role of de-clustering, the completeness model, quarry contamination, border properties, stationarity, regional b-value and magnitude-dependent hypocentral depth. (author)

  12. Coupling Hydrodynamic and Wave Propagation Codes for Modeling of Seismic Waves recorded at the SPE Test.

    Science.gov (United States)

    Larmat, C. S.; Rougier, E.; Delorey, A.; Steedman, D. W.; Bradley, C. R.

    2016-12-01

    The goal of the Source Physics Experiment (SPE) is to bring empirical and theoretical advances to the problem of detection and identification of underground nuclear explosions. For this, the SPE program includes a strong modeling effort based on first principles calculations with the challenge to capture both the source and near-source processes and those taking place later in time as seismic waves propagate within complex 3D geologic environments. In this paper, we report on results of modeling that uses hydrodynamic simulation codes (Abaqus and CASH) coupled with a 3D full waveform propagation code, SPECFEM3D. For modeling the near source region, we employ a fully-coupled Euler-Lagrange (CEL) modeling capability with a new continuum-based visco-plastic fracture model for simulation of damage processes, called AZ_Frac. These capabilities produce high-fidelity models of various factors believed to be key in the generation of seismic waves: the explosion dynamics, a weak grout-filled borehole, the surrounding jointed rock, and damage creation and deformations happening around the source and the free surface. SPECFEM3D, based on the Spectral Element Method (SEM) is a direct numerical method for full wave modeling with mathematical accuracy. The coupling interface consists of a series of grid points of the SEM mesh situated inside of the hydrodynamic code's domain. Displacement time series at these points are computed using output data from CASH or Abaqus (by interpolation if needed) and fed into the time marching scheme of SPECFEM3D. We will present validation tests with the Sharpe's model and comparisons of waveforms modeled with Rg waves (2-8Hz) that were recorded up to 2 km for SPE. We especially show effects of the local topography, velocity structure and spallation. Our models predict smaller amplitudes of Rg waves for the first five SPE shots compared to pure elastic models such as Denny &Johnson (1991).

  13. Seismo-thermo-mechanical modeling of subduction zone seismicity

    Energy Technology Data Exchange (ETDEWEB)

    Dinther van, Y.

    2013-07-01

    The catastrophic occurrence of the 2004 M9.2 Sumatra and 2011 M9.0 Tohoku earthquakes illustrated the disastrous impact of megathrust earthquakes on society. They also emphasized our limited understanding of where and when these 'big ones' may strike. The necessary improvement of long-term seismic hazard assessment requires a better physical understanding of the seismic cycle at these seismically active subduction zones. Models have the potential to overcome the restricted, direct observations in space and time. Currently, however, no model exists to explore the relation between long-term subduction dynamics and relating deformation and short-term seismogenesis. The development, validation and initial application of such a physically consistent seismo-thermo-mechanical numerical model is the main objective of this thesis. First, I present a novel analog modeling tool that simulates cycling of megathrust earthquakes in a visco-elastic gelatin wedge. A comparison with natural observations shows interseismic and coseismic physics are captured in a robust, albeit simplified, way. This tool is used to validate that a continuum-mechanics based, visco-elasto-plastic numerical approach, typically used for large-scale geodynamic problems, can be extended to study the short-term seismogenesis of megathrust earthquakes. To generate frictional instabilities and match laboratory source parameters, a local invariant implementation of a strongly slip rate-dependent friction formulation is required. The resulting continuum approach captures several interesting dynamic features, including inter-, co- and postseismic deformation that agrees qualitatively with GPS measurements and dynamic rupture features, including cracks, self-healing pulses and fault re-rupturing. To facilitate a comparison to natural settings, I consider a more realistic setup of the Southern Chilean margin in terms of geometry and physical processes. Results agree with seismological, geodetic and

  14. Seismo-thermo-mechanical modeling of subduction zone seismicity

    International Nuclear Information System (INIS)

    Dinther van, Y.

    2013-01-01

    The catastrophic occurrence of the 2004 M9.2 Sumatra and 2011 M9.0 Tohoku earthquakes illustrated the disastrous impact of megathrust earthquakes on society. They also emphasized our limited understanding of where and when these 'big ones' may strike. The necessary improvement of long-term seismic hazard assessment requires a better physical understanding of the seismic cycle at these seismically active subduction zones. Models have the potential to overcome the restricted, direct observations in space and time. Currently, however, no model exists to explore the relation between long-term subduction dynamics and relating deformation and short-term seismogenesis. The development, validation and initial application of such a physically consistent seismo-thermo-mechanical numerical model is the main objective of this thesis. First, I present a novel analog modeling tool that simulates cycling of megathrust earthquakes in a visco-elastic gelatin wedge. A comparison with natural observations shows interseismic and coseismic physics are captured in a robust, albeit simplified, way. This tool is used to validate that a continuum-mechanics based, visco-elasto-plastic numerical approach, typically used for large-scale geodynamic problems, can be extended to study the short-term seismogenesis of megathrust earthquakes. To generate frictional instabilities and match laboratory source parameters, a local invariant implementation of a strongly slip rate-dependent friction formulation is required. The resulting continuum approach captures several interesting dynamic features, including inter-, co- and postseismic deformation that agrees qualitatively with GPS measurements and dynamic rupture features, including cracks, self-healing pulses and fault re-rupturing. To facilitate a comparison to natural settings, I consider a more realistic setup of the Southern Chilean margin in terms of geometry and physical processes. Results agree with seismological, geodetic and geological

  15. Development of 3-axis precise positioning seismic physical modeling system in the simulation of marine seismic exploration

    Science.gov (United States)

    Kim, D.; Shin, S.; Ha, J.; Lee, D.; Lim, Y.; Chung, W.

    2017-12-01

    Seismic physical modeling is a laboratory-scale experiment that deals with the actual and physical phenomena that may occur in the field. In seismic physical modeling, field conditions are downscaled and used. For this reason, even a small error may lead to a big error in an actual field. Accordingly, the positions of the source and the receiver must be precisely controlled in scale modeling. In this study, we have developed a seismic physical modeling system capable of precisely controlling the 3-axis position. For automatic and precise position control of an ultrasonic transducer(source and receiver) in the directions of the three axes(x, y, and z), a motor was mounted on each of the three axes. The motor can automatically and precisely control the positions with positional precision of 2''; for the x and y axes and 0.05 mm for the z axis. As it can automatically and precisely control the positions in the directions of the three axes, it has an advantage in that simulations can be carried out using the latest exploration techniques, such as OBS and Broadband Seismic. For the signal generation section, a waveform generator that can produce a maximum of two sources was used, and for the data acquisition section, which receives and stores reflected signals, an A/D converter that can receive a maximum of four signals was used. As multiple sources and receivers could be used at the same time, the system was set up in such a way that diverse exploration methods, such as single channel, multichannel, and 3-D exploration, could be realized. A computer control program based on LabVIEW was created, so that it could control the position of the transducer, determine the data acquisition parameters, and check the exploration data and progress in real time. A marine environment was simulated using a water tank 1 m wide, 1 m long, and 0.9 m high. To evaluate the performance and applicability of the seismic physical modeling system developed in this study, single channel and

  16. Broadband seismic : case study modeling and data processing

    Science.gov (United States)

    Cahyaningtyas, M. B.; Bahar, A.

    2018-03-01

    Seismic data with wide range of frequency is needed due to its close relation to resolution and the depth of the target. Low frequency provides deeper penetration for the imaging of deep target. In addition, the wider the frequency bandwidth, the sharper the wavelet. Sharp wavelet is responsible for high-resolution imaging and is very helpful to resolve thin bed. As a result, the demand for broadband seismic data is rising and it spurs the technology development of broadband seismic in oil and gas industry. An obstacle that is frequently found on marine seismic data is the existence of ghost that affects the frequency bandwidth contained on the seismic data. Ghost alters bandwidth to bandlimited. To reduce ghost effect and to acquire broadband seismic data, lots of attempts are used, both on the acquisition and on the processing of seismic data. One of the acquisition technique applied is the multi-level streamer, where some streamers are towed on some levels of depth. Multi-level streamer will yield data with varied ghost notch shown on frequency domain. If the ghost notches are not overlapping, the summation of multi-level streamer data will reduce the ghost effect. The result of the multi-level streamer data processing shows that reduction of ghost notch on frequency domain indeed takes place.

  17. Seismic analysis of the APR1400 nuclear reactor system using a verified beam element model

    International Nuclear Information System (INIS)

    Park, Jong-beom; Park, No-Cheol; Lee, Sang-Jeong; Park, Young-Pil; Choi, Youngin

    2017-01-01

    Highlights: • A simplified beam element model is constructed based on the real dynamic characteristics of the APR1400. • Time history analysis is performed to calculate the seismic responses of the structures. • Large deformations can be observed at the in-phase mode of reactor vessel and core support barrel. - Abstract: Structural integrity is the first priority in the design of nuclear reactor internal structures. In particular, nuclear reactor internals should be designed to endure external forces, such as those due to earthquakes. Many researchers have performed finite element analyses to meet these design requirements. Generally, a seismic analysis model should reflect the dynamic characteristics of the target system. However, seismic analysis based on the finite element method requires long computation times as well as huge storage space. In this research, a beam element model was developed and confirmed based on the real dynamic characteristics of an advanced pressurized water nuclear reactor 1400 (APR1400) system. That verification process enhances the accuracy of the finite element analysis using the beam elements, remarkably. Also, the beam element model reduces seismic analysis costs. Therefore, the beam element model was used to perform the seismic analysis. Then, the safety of the APR1400 was assessed based on a seismic analysis of the time history responses of its structures. Thus, efficient, accurate seismic analysis was demonstrated using the proposed beam element model.

  18. Seismic analysis of the APR1400 nuclear reactor system using a verified beam element model

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong-beom [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Park, No-Cheol, E-mail: pnch@yonsei.ac.kr [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Lee, Sang-Jeong; Park, Young-Pil [Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722 (Korea, Republic of); Choi, Youngin [Korea Institute of Nuclear Safety, 62 Gwahak-ro, Yuseong-gu, Daejeon 34142 (Korea, Republic of)

    2017-03-15

    Highlights: • A simplified beam element model is constructed based on the real dynamic characteristics of the APR1400. • Time history analysis is performed to calculate the seismic responses of the structures. • Large deformations can be observed at the in-phase mode of reactor vessel and core support barrel. - Abstract: Structural integrity is the first priority in the design of nuclear reactor internal structures. In particular, nuclear reactor internals should be designed to endure external forces, such as those due to earthquakes. Many researchers have performed finite element analyses to meet these design requirements. Generally, a seismic analysis model should reflect the dynamic characteristics of the target system. However, seismic analysis based on the finite element method requires long computation times as well as huge storage space. In this research, a beam element model was developed and confirmed based on the real dynamic characteristics of an advanced pressurized water nuclear reactor 1400 (APR1400) system. That verification process enhances the accuracy of the finite element analysis using the beam elements, remarkably. Also, the beam element model reduces seismic analysis costs. Therefore, the beam element model was used to perform the seismic analysis. Then, the safety of the APR1400 was assessed based on a seismic analysis of the time history responses of its structures. Thus, efficient, accurate seismic analysis was demonstrated using the proposed beam element model.

  19. Ground motion models used in the 2014 U.S. National Seismic Hazard Maps

    Science.gov (United States)

    Rezaeian, Sanaz; Petersen, Mark D.; Moschetti, Morgan P.

    2015-01-01

    The National Seismic Hazard Maps (NSHMs) are an important component of seismic design regulations in the United States. This paper compares hazard using the new suite of ground motion models (GMMs) relative to hazard using the suite of GMMs applied in the previous version of the maps. The new source characterization models are used for both cases. A previous paper (Rezaeian et al. 2014) discussed the five NGA-West2 GMMs used for shallow crustal earthquakes in the Western United States (WUS), which are also summarized here. Our focus in this paper is on GMMs for earthquakes in stable continental regions in the Central and Eastern United States (CEUS), as well as subduction interface and deep intraslab earthquakes. We consider building code hazard levels for peak ground acceleration (PGA), 0.2-s, and 1.0-s spectral accelerations (SAs) on uniform firm-rock site conditions. The GMM modifications in the updated version of the maps created changes in hazard within 5% to 20% in WUS; decreases within 5% to 20% in CEUS; changes within 5% to 15% for subduction interface earthquakes; and changes involving decreases of up to 50% and increases of up to 30% for deep intraslab earthquakes for most U.S. sites. These modifications were combined with changes resulting from modifications in the source characterization models to obtain the new hazard maps.

  20. Regional relationships among earthquake magnitude scales. Seismic safety margins research program

    International Nuclear Information System (INIS)

    Chung, D.H.; Bernreuter, D.L.

    1980-09-01

    The seismic body-wave magnitude m b of an earthquake is strongly affected by regional variations in the Q structure, composition, and physical state within the earth. Therefore, because of differences in attenuation of P-waves between the western and eastern United States, a problem arises when comparing m b 's for the two regions. A regional m b magnitude bias exists which, depending on where the earthquake occurs and where the P-waves are recorded, can lead to magnitude errors as large as one-third unit. There is also a significant difference between m b and M L values for earthquakes in the western United States. An empirical link between the m b of an eastern U.S. earthquake and the M L of an equivalent western earthquake is given y M L = 0.57 + 0.92(m b ) East . This result is important when comparing ground motion between the two regions and for choosing a set of real western U.S. earthquake records to represent eastern earthquakes. (author)

  1. When probabilistic seismic hazard climbs volcanoes: the Mt. Etna case, Italy - Part 1: Model components for sources parameterization

    Science.gov (United States)

    Azzaro, Raffaele; Barberi, Graziella; D'Amico, Salvatore; Pace, Bruno; Peruzza, Laura; Tuvè, Tiziana

    2017-11-01

    The volcanic region of Mt. Etna (Sicily, Italy) represents a perfect lab for testing innovative approaches to seismic hazard assessment. This is largely due to the long record of historical and recent observations of seismic and tectonic phenomena, the high quality of various geophysical monitoring and particularly the rapid geodynamics clearly demonstrate some seismotectonic processes. We present here the model components and the procedures adopted for defining seismic sources to be used in a new generation of probabilistic seismic hazard assessment (PSHA), the first results and maps of which are presented in a companion paper, Peruzza et al. (2017). The sources include, with increasing complexity, seismic zones, individual faults and gridded point sources that are obtained by integrating geological field data with long and short earthquake datasets (the historical macroseismic catalogue, which covers about 3 centuries, and a high-quality instrumental location database for the last decades). The analysis of the frequency-magnitude distribution identifies two main fault systems within the volcanic complex featuring different seismic rates that are controlled essentially by volcano-tectonic processes. We discuss the variability of the mean occurrence times of major earthquakes along the main Etnean faults by using an historical approach and a purely geologic method. We derive a magnitude-size scaling relationship specifically for this volcanic area, which has been implemented into a recently developed software tool - FiSH (Pace et al., 2016) - that we use to calculate the characteristic magnitudes and the related mean recurrence times expected for each fault. Results suggest that for the Mt. Etna area, the traditional assumptions of uniform and Poissonian seismicity can be relaxed; a time-dependent fault-based modeling, joined with a 3-D imaging of volcano-tectonic sources depicted by the recent instrumental seismicity, can therefore be implemented in PSHA maps

  2. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    Science.gov (United States)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  3. Adaptive neuro-fuzzy inference systems for semi-automatic discrimination between seismic events: a study in Tehran region

    Science.gov (United States)

    Vasheghani Farahani, Jamileh; Zare, Mehdi; Lucas, Caro

    2012-04-01

    Thisarticle presents an adaptive neuro-fuzzy inference system (ANFIS) for classification of low magnitude seismic events reported in Iran by the network of Tehran Disaster Mitigation and Management Organization (TDMMO). ANFIS classifiers were used to detect seismic events using six inputs that defined the seismic events. Neuro-fuzzy coding was applied using the six extracted features as ANFIS inputs. Two types of events were defined: weak earthquakes and mining blasts. The data comprised 748 events (6289 signals) ranging from magnitude 1.1 to 4.6 recorded at 13 seismic stations between 2004 and 2009. We surveyed that there are almost 223 earthquakes with M ≤ 2.2 included in this database. Data sets from the south, east, and southeast of the city of Tehran were used to evaluate the best short period seismic discriminants, and features as inputs such as origin time of event, distance (source to station), latitude of epicenter, longitude of epicenter, magnitude, and spectral analysis (fc of the Pg wave) were used, increasing the rate of correct classification and decreasing the confusion rate between weak earthquakes and quarry blasts. The performance of the ANFIS model was evaluated for training and classification accuracy. The results confirmed that the proposed ANFIS model has good potential for determining seismic events.

  4. Statistical Analysis and ETAS Modeling of Seismicity Induced by Production of Geothermal Energy from Hydrothermal Systems

    Science.gov (United States)

    Dinske, C.; Langenbruch, C.; Shapiro, S. A.

    2017-12-01

    We investigate seismicity related to hydrothermal systems in Germany and Italy, focussing on temporal changes of seismicity rates. Our analysis was motivated by numerical simulations The modeling of stress changes caused by the injection and production of fluid revealed that seismicity rates decrease on a long-term perspective which is not observed in the considered case studies. We analyze the waiting time distributions of the seismic events in both time domain (inter event times) and fluid volume domain (inter event volume). We find clear indications that the observed seismicity comprises two components: (1) seismicity that is directly triggered by production and re-injection of fluid, i.e. induced events, and (2) seismicity that is triggered by earthquake interactions, i.e. aftershock triggering. In order to better constrain our numerical simulations using the observed induced seismicity we apply catalog declustering to seperate the two components. We use the magnitude-dependent space-time windowing approach introduced by Gardner and Knopoff (1974) and test several published algorithms to calculate the space-time windows. After declustering, we conclude that the different hydrothermal reservoirs show a comparable seismic response to the circulation of fluid and additional triggering by earthquake interactions. The declustered catalogs contain approximately 50 per cent of the number of events in the original catalogs. We then perform ETAS (Epidemic Type Aftershock; Ogata, 1986, 1988) modeling for two reasons. First, we want to know whether the different reservoirs are also comparable regarding earthquake interaction patterns. Second, if we identify systematic patterns, ETAS modeling can contribute to forecast seismicity during production of geothermal energy. We find that stationary ETAS models cannot accurately capture real seismicity rate changes. One reason for this finding is given by the rate of observed induced events which is not constant over time. Hence

  5. Spectral-Element Seismic Wave Propagation Codes for both Forward Modeling in Complex Media and Adjoint Tomography

    Science.gov (United States)

    Smith, J. A.; Peter, D. B.; Tromp, J.; Komatitsch, D.; Lefebvre, M. P.

    2015-12-01

    We present both SPECFEM3D_Cartesian and SPECFEM3D_GLOBE open-source codes, representing high-performance numerical wave solvers simulating seismic wave propagation for local-, regional-, and global-scale application. These codes are suitable for both forward propagation in complex media and tomographic imaging. Both solvers compute highly accurate seismic wave fields using the continuous Galerkin spectral-element method on unstructured meshes. Lateral variations in compressional- and shear-wave speeds, density, as well as 3D attenuation Q models, topography and fluid-solid coupling are all readily included in both codes. For global simulations, effects due to rotation, ellipticity, the oceans, 3D crustal models, and self-gravitation are additionally included. Both packages provide forward and adjoint functionality suitable for adjoint tomography on high-performance computing architectures. We highlight the most recent release of the global version which includes improved performance, simultaneous MPI runs, OpenCL and CUDA support via an automatic source-to-source transformation library (BOAST), parallel I/O readers and writers for databases using ADIOS and seismograms using the recently developed Adaptable Seismic Data Format (ASDF) with built-in provenance. This makes our spectral-element solvers current state-of-the-art, open-source community codes for high-performance seismic wave propagation on arbitrarily complex 3D models. Together with these solvers, we provide full-waveform inversion tools to image the Earth's interior at unprecedented resolution.

  6. An asymptotic model of seismic reflection from a permeable layer

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Goloshubin, G.

    2009-10-15

    Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot's model of poroelasticity. A review of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and Darcy's law suggests an alternative new physical interpretation of some coefficients of the classical poroelasticity. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The absolute value of this parameter is equal to the product of the kinematic reservoir fluid mobility and the wave frequency. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). Practical applications of the obtained asymptotic formulae are seismic modeling, inversion, and at-tribute analysis.

  7. Stochastic Modelling as a Tool for Seismic Signals Segmentation

    Directory of Open Access Journals (Sweden)

    Daniel Kucharczyk

    2016-01-01

    Full Text Available In order to model nonstationary real-world processes one can find appropriate theoretical model with properties following the analyzed data. However in this case many trajectories of the analyzed process are required. Alternatively, one can extract parts of the signal that have homogenous structure via segmentation. The proper segmentation can lead to extraction of important features of analyzed phenomena that cannot be described without the segmentation. There is no one universal method that can be applied for all of the phenomena; thus novel methods should be invented for specific cases. They might address specific character of the signal in different domains (time, frequency, time-frequency, etc.. In this paper we propose two novel segmentation methods that take under consideration the stochastic properties of the analyzed signals in time domain. Our research is motivated by the analysis of vibration signals acquired in an underground mine. In such signals we observe seismic events which appear after the mining activity, like blasting, provoked relaxation of rock, and some unexpected events, like natural rock burst. The proposed segmentation procedures allow for extraction of such parts of the analyzed signals which are related to mentioned events.

  8. Computational Software to Fit Seismic Data Using Epidemic-Type Aftershock Sequence Models and Modeling Performance Comparisons

    Science.gov (United States)

    Chu, A.

    2016-12-01

    Modern earthquake catalogs are often analyzed using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). My work implements three of the homogeneous ETAS models described in Ogata (1998). With a model's log-likelihood function, my software finds the Maximum-Likelihood Estimates (MLEs) of the model's parameters to estimate the homogeneous background rate and the temporal and spatial parameters that govern triggering effects. EM-algorithm is employed for its advantages of stability and robustness (Veen and Schoenberg, 2008). My work also presents comparisons among the three models in robustness, convergence speed, and implementations from theory to computing practice. Up-to-date regional seismic data of seismic active areas such as Southern California and Japan are used to demonstrate the comparisons. Data analysis has been done using computer languages Java and R. Java has the advantages of being strong-typed and easiness of controlling memory resources, while R has the advantages of having numerous available functions in statistical computing. Comparisons are also made between the two programming languages in convergence and stability, computational speed, and easiness of implementation. Issues that may affect convergence such as spatial shapes are discussed.

  9. Seismic Ecology

    Science.gov (United States)

    Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

    The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

  10. Scale model study of the seismic response of a nuclear reactor core

    International Nuclear Information System (INIS)

    Dove, R.C.; Dunwoody, W.E.; Rhorer, R.L.

    1983-01-01

    The use of scale models to study the dynamics of a system of graphite core blocks used in certain nuclear reactor designs is described. Scaling laws, material selecton, model instrumentation to measure collision forces, and the response of several models to simulated seismic excitation are covered. The effects of Coulomb friction between the blocks and the clearance gaps between the blocks on the system response to seismic excitation are emphasized

  11. Preparing a seismic hazard model for Switzerland: the view from PEGASOS Expert Group 3 (EG1c)

    Energy Technology Data Exchange (ETDEWEB)

    Musson, R. M. W. [British Geological Survey, West Mains Road, Edinburgh, EH9 3LA (United Kingdom); Sellami, S. [Swiss Seismological Service, ETH-Hoenggerberg, Zuerich (Switzerland); Bruestle, W. [Regierungspraesidium Freiburg, Abt. 9: Landesamt fuer Geologie, Rohstoffe und Bergbau, Ref. 98: Landeserdbebendienst, Freiburg im Breisgau (Germany)

    2009-05-15

    The seismic hazard model used in the PEGASOS project for assessing earth-quake hazard at four NPP sites was a composite of four sub-models, each produced by a team of three experts. In this paper, one of these models is described in detail by the authors. A criticism sometimes levelled at probabilistic seismic hazard studies is that the process by which seismic source zones are arrived at is obscure, subjective and inconsistent. Here, we attempt to recount the stages by which the model evolved, and the decisions made along the way. In particular, a macro-to-micro approach was used, in which three main stages can be described. The first was the characterisation of the overall kinematic model, the 'big picture' of regional seismo-genesis. Secondly, this was refined to a more detailed seismotectonic model. Lastly, this was used as the basis of individual sources, for which parameters can be assessed. Some basic questions had also to be answered about aspects of the approach to modelling to be used: for instance, is spatial smoothing an appropriate tool to apply? Should individual fault sources be modelled in an intra-plate environment? Also, the extent to which alternative modelling decisions should be expressed in a logic tree structure has to be considered. (author)

  12. Preparing a seismic hazard model for Switzerland: the view from PEGASOS Expert Group 3 (EG1c)

    International Nuclear Information System (INIS)

    Musson, R. M. W.; Sellami, S.; Bruestle, W.

    2009-01-01

    The seismic hazard model used in the PEGASOS project for assessing earth-quake hazard at four NPP sites was a composite of four sub-models, each produced by a team of three experts. In this paper, one of these models is described in detail by the authors. A criticism sometimes levelled at probabilistic seismic hazard studies is that the process by which seismic source zones are arrived at is obscure, subjective and inconsistent. Here, we attempt to recount the stages by which the model evolved, and the decisions made along the way. In particular, a macro-to-micro approach was used, in which three main stages can be described. The first was the characterisation of the overall kinematic model, the 'big picture' of regional seismo-genesis. Secondly, this was refined to a more detailed seismotectonic model. Lastly, this was used as the basis of individual sources, for which parameters can be assessed. Some basic questions had also to be answered about aspects of the approach to modelling to be used: for instance, is spatial smoothing an appropriate tool to apply? Should individual fault sources be modelled in an intra-plate environment? Also, the extent to which alternative modelling decisions should be expressed in a logic tree structure has to be considered. (author)

  13. Hypocenter relocation along the Sunda arc in Indonesia, using a 3D seismic velocity model

    Science.gov (United States)

    Nugraha, Andri Dian; Shiddiqi, Hasbi A.; Widiyantoro, Sri; Thurber, Clifford H.; Pesicek, Jeremy D.; Zhang, Haijiang; Wiyono, Samsul H.; Ramadhan, Mohamad; Wandano,; Irsyam, Mahsyur

    2018-01-01

    The tectonics of the Sunda arc region is characterized by the junction of the Eurasian and Indo‐Australian tectonic plates, causing complex dynamics to take place. High‐seismicity rates in the Indonesian region occur due to the interaction between these tectonic plates. The availability of a denser network of seismometers after the earthquakes of Mw">Mw 9.1 in 2004 and  Mw">Mw 8.6 in 2005 supports various seismic studies, one of which regards the precise relocation of the hypocenters. In this study, hypocenter relocation was performed using a teleseismic double‐difference (DD) relocation method (teletomoDD) combining arrival times of P and S waves from stations at local, regional, and teleseismic distances. The catalog data were taken from the Agency of Meteorology, Climatology, and Geophysics (BMKG) of Indonesia, and the International Seismological Centre (ISC) for the time period of April 2009 to May 2015. The 3D seismic‐wave velocity model with a grid size 1°×1°">1°×1° was used in the travel‐time calculations. Relocation results show a reduction in travel‐time residuals compared with the initial locations. The relocation results better illuminate subducted slabs and active faults in the region such as the Mentawai back thrust and the outer rise in the subduction zone south of Java. Focal mechanisms from the Global Centroid Moment Tensor catalog are analyzed in conjunction with the relocation results, and our synthesis of the results provides further insight into seismogenesis in the region.

  14. Probabilistic Seismic Performance Model for Tunnel Form Concrete Building Structures

    Directory of Open Access Journals (Sweden)

    S. Bahram Beheshti Aval

    2016-12-01

    Full Text Available Despite widespread construction of mass-production houses with tunnel form structural system across the world, unfortunately no special seismic code is published for design of this type of construction. Through a literature survey, only a few studies are about the seismic behavior of this type of structural system. Thus based on reasonable numerical results, the seismic performance of structures constructed with this technique considering the effective factors on structural behavior is highly noteworthy in a seismic code development process. In addition, due to newness of this system and observed damages in past earthquakes, and especially random nature of future earthquakes, the importance of probabilistic approach and necessity of developing fragility curves in a next generation Performance Based Earthquake Engineering (PBEE frame work are important. In this study, the seismic behavior of 2, 5 and 10 story tunnel form structures with a regular plan is examined. First, the performance levels of these structures under the design earthquake (return period of 475 years with time history analysis and pushover method are assessed, and then through incremental dynamic analysis, fragility curves are extracted for different levels of damage in walls and spandrels. The results indicated that the case study structures have high capacity and strength and show appropriate seismic performance. Moreover, all three structures subjected were in immediate occupancy performance level.

  15. Method for inverting reflection trace data from 3-D and 4-D seismic surveys and identifying subsurface fluid and pathways in and among hydrocarbon reservoirs based on impedance models

    Science.gov (United States)

    He, W.; Anderson, R.N.

    1998-08-25

    A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management. 20 figs.

  16. A model of seismic focus and related statistical distributions of earthquakes

    International Nuclear Information System (INIS)

    Apostol, Bogdan-Felix

    2006-01-01

    A growth model for accumulating seismic energy in a localized seismic focus is described, which introduces a fractional parameter r on geometrical grounds. The model is employed for deriving a power-type law for the statistical distribution in energy, where the parameter r contributes to the exponent, as well as corresponding time and magnitude distributions for earthquakes. The accompanying seismic activity of foreshocks and aftershocks is discussed in connection with this approach, as based on Omori distributions, and the rate of released energy is derived

  17. Seismic soil structure interaction: analysis and centrifuge model studies

    International Nuclear Information System (INIS)

    Finn, W.D.L.; Ledbetter, R.H.; Beratan, L.L.

    1985-01-01

    A method for non-linear dynamic effective stress analysis is introduced which is applicable to soil-structure interaction problems. Full interaction including slip between structure and foundation is taken into account and the major factors are included which must be considered when computing dynamic soil response. An experimental investigation was conducted using simulated earthquake tests on centrifuged geotechnical models in order to obtain prototype response data of foundation soils carrying both surface and embedded structures and to validate the dynamic effective stress analysis. Horizontal and vertical accelerations were measured at various points on structures and in the sand foundation. Seismically-induced pore water pressure changes were also measured at various locations in the foundation. Computer plots of the data were obtained while the centrifuge was in flight and representative samples are presented. The results show clearly the pronounced effect that increasing pore water pressures have on dynamic response. It is demonstrated that a coherent picture of dynamic response of soil-structure systems is provided by dynamic effective stress non-linear analysis. Based on preliminary results, it appears that the pore water pressure effects can be predicted

  18. Seismic soil-structure interaction: Analysis and centrifuge model studies

    International Nuclear Information System (INIS)

    Finn, W.D.L.; Ledbetter, R.H.; Beratan, L.L.

    1986-01-01

    A method for nonlinear dynamic effective stress analysis applicable to soil-structure interaction problems is introduced. Full interaction including slip between structure and foundation is taken into account and the major factors that must be considered when computing dynamic soil response are included. An experimental investigation using simulated earthquake tests on centrifuged geotechnical models was conducted to obtain prototype response data of foundation soils carrying both surface and embedded structures and to validate the dynamic effective stress analysis. The centrifuge tests were conducted in the Geotechnical Centrifuge at Cambridge University, England. Horizontal and vertical accelerations were measured at various points on structures and in the sand foundation. Seismically induced pore water pressure changes were also measured at various locations in the foundation. Computer plots of the data were obtained while the centrifuge was in flight and representative samples are presented. The results clearly show the pronounced effect of increasing pore water pressures on dynamic response. It is demonstrated that a coherent picture of dynamic response of soil-structure systems is provided by dynamic effective stress nonlinear analysis. On the basis of preliminary results, it appears that the effects of pore water pressure can be predicted. (orig.)

  19. A robust absorbing layer method for anisotropic seismic wave modeling

    Energy Technology Data Exchange (ETDEWEB)

    Métivier, L., E-mail: ludovic.metivier@ujf-grenoble.fr [LJK, CNRS, Université de Grenoble, BP 53, 38041 Grenoble Cedex 09 (France); ISTerre, Université de Grenoble I, BP 53, 38041 Grenoble Cedex 09 (France); Brossier, R. [ISTerre, Université de Grenoble I, BP 53, 38041 Grenoble Cedex 09 (France); Labbé, S. [LJK, CNRS, Université de Grenoble, BP 53, 38041 Grenoble Cedex 09 (France); Operto, S. [Géoazur, Université de Nice Sophia-Antipolis, CNRS, IRD, OCA, Villefranche-sur-Mer (France); Virieux, J. [ISTerre, Université de Grenoble I, BP 53, 38041 Grenoble Cedex 09 (France)

    2014-12-15

    When applied to wave propagation modeling in anisotropic media, Perfectly Matched Layers (PML) exhibit instabilities. Incoming waves are amplified instead of being absorbed. Overcoming this difficulty is crucial as in many seismic imaging applications, accounting accurately for the subsurface anisotropy is mandatory. In this study, we present the SMART layer method as an alternative to PML approach. This method is based on the decomposition of the wavefield into components propagating inward and outward the domain of interest. Only outgoing components are damped. We show that for elastic and acoustic wave propagation in Transverse Isotropic media, the SMART layer is unconditionally dissipative: no amplification of the wavefield is possible. The SMART layers are not perfectly matched, therefore less accurate than conventional PML. However, a reasonable increase of the layer size yields an accuracy similar to PML. Finally, we illustrate that the selective damping strategy on which is based the SMART method can prevent the generation of spurious S-waves by embedding the source in a small zone where only S-waves are damped.

  20. A robust absorbing layer method for anisotropic seismic wave modeling

    International Nuclear Information System (INIS)

    Métivier, L.; Brossier, R.; Labbé, S.; Operto, S.; Virieux, J.

    2014-01-01

    When applied to wave propagation modeling in anisotropic media, Perfectly Matched Layers (PML) exhibit instabilities. Incoming waves are amplified instead of being absorbed. Overcoming this difficulty is crucial as in many seismic imaging applications, accounting accurately for the subsurface anisotropy is mandatory. In this study, we present the SMART layer method as an alternative to PML approach. This method is based on the decomposition of the wavefield into components propagating inward and outward the domain of interest. Only outgoing components are damped. We show that for elastic and acoustic wave propagation in Transverse Isotropic media, the SMART layer is unconditionally dissipative: no amplification of the wavefield is possible. The SMART layers are not perfectly matched, therefore less accurate than conventional PML. However, a reasonable increase of the layer size yields an accuracy similar to PML. Finally, we illustrate that the selective damping strategy on which is based the SMART method can prevent the generation of spurious S-waves by embedding the source in a small zone where only S-waves are damped

  1. Subsurface geology of the Lusi region: preliminary results from a comprehensive seismic-stratigraphic study.

    Science.gov (United States)

    Moscariello, Andrea; Do Couto, Damien; Lupi, Matteo; Mazzini, Adriano

    2016-04-01

    We investigate the subsurface data of a large sector in the Sidoarjo district (East Java, Indonesia) where the sudden catastrophic Lusi eruption started the 26th May 2006. Our goal is to understand the stratigraphic and structural features which can be genetically related to the surface manifestations of deep hydrothermal fluids and thus allow us to predict possible future similar phenomena in the region. In the framework of the Lusi Lab project (ERC grant n° 308126) we examined a series of densely spaced 2D reflection commercial seismic lines This allowed the reconstruction of the lateral variability of key stratigraphic horizons as well as the main tectonic features. In particular, we shed light on the deep structure of the Watukosek fault system and the associated fracture corridors crossing the entire stratigraphic successions. To the South-West, when approaching the volcanic complex, we could identify a clear contrast in seismic facies between chaotic volcanoclastic wedges and clastic-prone sedimentary successions as well as between the deeper stratigraphic units consisting of carbonates and lateral shales units. The latter show possible ductile deformation associated to fault-controlled diapirism which control in turns deformation of overlying stratigraphic units and deep geo-fluids circulation. Large collapse structures recognized in the study area (e.g. well PRG-1) are interpreted as the results of shale movement at depth. Similarly to Lusi, vertical deformation zones ("pipes"), likely associated with deeply rooted strike-slip systems seem to be often located at the interface between harder carbonate rocks forming isolated build ups and the laterally nearby clastic (shale-prone)-units. The mechanisms of deformation of structural features (strike vs dip slip systems) which may affect either the basement rock or the overlying deeper stratigraphic rocks is also being investigated to understand the relationship between deep and shallower (i.e. meteoric) fluid

  2. Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs

    Science.gov (United States)

    We have conducted numerical simulation studies to assess the potential for injection-induced fault reactivation and notable seismic events associated with shale-gas hydraulic fracturing operations. The modeling is generally tuned toward conditions usually encountered in the Marce...

  3. New tomographic images of P- , S- wave velocity and Q on the Philippine Sea Slab beneath Tokyo: Implication to seismotectonics and seismic hazard in the Tokyo metropolitan region

    Science.gov (United States)

    Hirata, Naoshi; Sakai, Shin'ichi; Nakagawa, Shigeki; Panayotopoulos, Yannis; Ishikawa, Masahiro; Sato, Hiroshi; Kasahara, Keiji; Kimura, Hisanor; Honda, Ryou

    2013-04-01

    The Central Disaster Management Council of Japan estimates the next great M7+ earthquake in the Tokyo metropolitan region will cause 11,000 fatalities and 112 trillion yen (1 trillion US) economic loss at worst case if it occur beneath northern Tokyo bay with M7.3. However, the estimate is based on a source fault model by conventional studies about the PSP geometry. To evaluate seismic hazard due to the great quake we need to clarify the geometry of PSP and also the Pacific palate (PAP) that subducs beneath PSP. We identify those plates with use of seismic tomography and available deep seismic reflection profiling and borehole data in southern Kanto area. We deployed about 300 seismic stations in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area. We obtain clear P- and S- wave velocity (Vp and Vs) and Q tomograms which show a clear image of PSP and PAP. A depth to the top of PSP, 20 to 30 kilometer beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo region. Based on elastic wave velocities of rocks and minerals, we interpreted the tomographic images as petrologic images. Tomographic images revealed the presence of two stepwise velocity increase of the top layer of the subducting PSP slab. Rock velocity data reveals that subducting PSP crust transforms from blueschists to amphibolites at depth of 30km and amphibolites to eclogites at depth of 50km, which suggest that dehydration reactions occurs in subducting crust of basaltic compositions during prograde metamorphism and water is released from the subducting PSP crust. Tomograms show evidence for a low-velocity zone (LVZ) beneath the area just north of Tokyo bay. A Q tomogram show a low Q zone in PSP slab. We interpret the LVZ as a

  4. Robust seismicity forecasting based on Bayesian parameter estimation for epidemiological spatio-temporal aftershock clustering models.

    Science.gov (United States)

    Ebrahimian, Hossein; Jalayer, Fatemeh

    2017-08-29

    In the immediate aftermath of a strong earthquake and in the presence of an ongoing aftershock sequence, scientific advisories in terms of seismicity forecasts play quite a crucial role in emergency decision-making and risk mitigation. Epidemic Type Aftershock Sequence (ETAS) models are frequently used for forecasting the spatio-temporal evolution of seismicity in the short-term. We propose robust forecasting of seismicity based on ETAS model, by exploiting the link between Bayesian inference and Markov Chain Monte Carlo Simulation. The methodology considers the uncertainty not only in the model parameters, conditioned on the available catalogue of events occurred before the forecasting interval, but also the uncertainty in the sequence of events that are going to happen during the forecasting interval. We demonstrate the methodology by retrospective early forecasting of seismicity associated with the 2016 Amatrice seismic sequence activities in central Italy. We provide robust spatio-temporal short-term seismicity forecasts with various time intervals in the first few days elapsed after each of the three main events within the sequence, which can predict the seismicity within plus/minus two standard deviations from the mean estimate within the few hours elapsed after the main event.

  5. The smart cluster method. Adaptive earthquake cluster identification and analysis in strong seismic regions

    Science.gov (United States)

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann

    2017-07-01

    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  6. Yield Estimation for Semipalatinsk Underground Nuclear Explosions Using Seismic Surface-wave Observations at Near-regional Distances

    Science.gov (United States)

    Adushkin, V. V.

    - A statistical procedure is described for estimating the yields of underground nuclear tests at the former Soviet Semipalatinsk test site using the peak amplitudes of short-period surface waves observed at near-regional distances (Δ Semipalatinsk explosions, including the Soviet JVE explosion of September 14, 1988, and it is demonstrated that it provides seismic estimates of explosion yield which are typically within 20% of the yields determined for these same explosions using more accurate, non-seismic techniques based on near-source observations.

  7. Comparison of Omega-2 and Omega-3 calibration explosions basing on regional seismic data

    International Nuclear Information System (INIS)

    Mikhajlova, N.N.; Sokolova, I.N.

    2001-01-01

    Comparison of different parameters of seismic records of Omega-2 and Omega-3 calibration explosions was performed. It was shown that despite the equal charge the level of seismic oscillations was lower during the Omega-3 explosion than during Omega-2. Spectral composition, polarization of oscillations, wave picture is identical at a given station for both explosions. Assumptions were made on the reason of such difference in seismic effect. (author)

  8. Installation of a digital, wireless, strong-motion network for monitoring seismic activity in a western Colorado coal mining region

    Energy Technology Data Exchange (ETDEWEB)

    Peter Swanson; Collin Stewart; Wendell Koontz [NIOSH, Spokane, WA (USA). Spokane Research Laboratory

    2007-01-15

    A seismic monitoring network has recently been installed in the North Fork Valley coal mining region of western Colorado as part of a NIOSH mine safety technology transfer project with two longwall coal mine operators. Data recorded with this network will be used to characterize mining related and natural seismic activity in the vicinity of the mines and examine potential hazards due to ground shaking near critical structures such as impoundment dams, reservoirs, and steep slopes. Ten triaxial strong-motion accelerometers have been installed on the surface to form the core of a network that covers approximately 250 square kilometers (100 sq. miles) of rugged canyon-mesa terrain. Spread-spectrum radio networks are used to telemeter continuous streams of seismic waveform data to a central location where they are converted to IP data streams and ported to the Internet for processing, archiving, and analysis. 4 refs.

  9. Seismic analysis of a reinforced concrete containment vessel model

    International Nuclear Information System (INIS)

    Randy, James J.; Cherry, Jeffery L.; Rashid, Yusef R.; Chokshi, Nilesh

    2000-01-01

    Pre-and post-test analytical predictions of the dynamic behavior of a 1:10 scale model Reinforced Concrete Containment Vessel are presented. This model, designed and constructed by the Nuclear Power Engineering Corp., was subjected to seismic simulation tests using the high-performance shaking table at the Tadotsu Engineering Laboratory in Japan. A group of tests representing design-level and beyond-design-level ground motions were first conducted to verify design safety margins. These were followed by a series of tests in which progressively larger base motions were applied until structural failure was induced. The analysis was performed by ANATECH Corp. and Sandia National Laboratories for the US Nuclear Regulatory Commission, employing state-of-the-art finite-element software specifically developed for concrete structures. Three-dimensional time-history analyses were performed, first as pre-test blind predictions to evaluate the general capabilities of the analytical methods, and second as post-test validation of the methods and interpretation of the test result. The input data consisted of acceleration time histories for the horizontal, vertical and rotational (rocking) components, as measured by accelerometers mounted on the structure's basemat. The response data consisted of acceleration and displacement records for various points on the structure, as well as time-history records of strain gages mounted on the reinforcement. This paper reports on work in progress and presents pre-test predictions and post-test comparisons to measured data for tests simulating maximum design basis and extreme design basis earthquakes. The pre-test analyses predict the failure earthquake of the test structure to have an energy level in the range of four to five times the energy level of the safe shutdown earthquake. The post-test calculations completed so far show good agreement with measured data

  10. Resistivity and Seismic Surface Wave Tomography Results for the Nevşehir Kale Region: Cappadocia, Turkey

    Science.gov (United States)

    Coşkun, Nart; Çakır, Özcan; Erduran, Murat; Arif Kutlu, Yusuf

    2014-05-01

    The Nevşehir Kale region located in the middle of Cappadocia with approximately cone shape is investigated for existence of an underground city using the geophysical methods of electrical resistivity and seismic surface wave tomography together. Underground cities are generally known to exist in Cappadocia. The current study has obtained important clues that there may be another one under the Nevşehir Kale region. Two-dimensional resistivity and seismic profiles approximately 4-km long surrounding the Nevşehir Kale are measured to determine the distribution of electrical resistivities and seismic velocities under the profiles. Several high resistivity anomalies with a depth range 8-20 m are discovered to associate with a systematic void structure beneath the region. Because of the high resolution resistivity measurement system currently employed we were able to isolate the void structure from the embedding structure. Low seismic velocity zones associated with the high resistivity depths are also discovered. Using three-dimensional visualization techniques we show the extension of the void structure under the measured profiles.

  11. Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

    Science.gov (United States)

    Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

    2017-12-01

    Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

  12. Modeling of seismic hazards for dynamic reliability analysis

    International Nuclear Information System (INIS)

    Mizutani, M.; Fukushima, S.; Akao, Y.; Katukura, H.

    1993-01-01

    This paper investigates the appropriate indices of seismic hazard curves (SHCs) for seismic reliability analysis. In the most seismic reliability analyses of structures, the seismic hazards are defined in the form of the SHCs of peak ground accelerations (PGAs). Usually PGAs play a significant role in characterizing ground motions. However, PGA is not always a suitable index of seismic motions. When random vibration theory developed in the frequency domain is employed to obtain statistics of responses, it is more convenient for the implementation of dynamic reliability analysis (DRA) to utilize an index which can be determined in the frequency domain. In this paper, we summarize relationships among the indices which characterize ground motions. The relationships between the indices and the magnitude M are arranged as well. In this consideration, duration time plays an important role in relating two distinct class, i.e. energy class and power class. Fourier and energy spectra are involved in the energy class, and power and response spectra and PGAs are involved in the power class. These relationships are also investigated by using ground motion records. Through these investigations, we have shown the efficiency of employing the total energy as an index of SHCs, which can be determined in the time and frequency domains and has less variance than the other indices. In addition, we have proposed the procedure of DRA based on total energy. (author)

  13. The 2016-2017 Central Italy Seismic Sequence: Source Complexity Inferred from Rupture Models.

    Science.gov (United States)

    Scognamiglio, L.; Tinti, E.; Casarotti, E.; Pucci, S.; Villani, F.; Cocco, M.; Magnoni, F.; Michelini, A.

    2017-12-01

    The Apennines have been struck by several seismic sequences in recent years, showing evidence of the activation of multiple segments of normal fault systems in a variable and, relatively short, time span, as in the case of the 1980 Irpinia earthquake (three shocks in 40 s), the 1997 Umbria-Marche sequence (four main shocks in 18 days) and the 2009 L'Aquila earthquake having three segments activated within a few weeks. The 2016-2017 central Apennines seismic sequence begin on August 24th with a MW 6.0 earthquake, which strike the region between Amatrice and Accumoli causing 299 fatalities. This earthquake ruptures a nearly 20 km long normal fault and shows a quite heterogeneous slip distribution. On October 26th, another main shock (MW 5.9) occurs near Visso extending the activated seismogenic area toward the NW. It is a double event rupturing contiguous patches on the fault segment of the normal fault system. Four days after the second main shock, on October 30th, a third earthquake (MW 6.5) occurs near Norcia, roughly midway between Accumoli and Visso. In this work we have inverted strong motion waveforms and GPS data to retrieve the source model of the MW 6.5 event with the aim of interpreting the rupture process in the framework of this complex sequence of moderate magnitude earthquakes. We noted that some preliminary attempts to model the slip distribution of the October 30th main shock using a single fault plane oriented along the Apennines did not provide convincing fits to the observed waveforms. In addition, the deformation pattern inferred from satellite observations suggested the activation of a multi-fault structure, that is coherent to the complexity and the extension of the geological surface deformation. We investigated the role of multi-fault ruptures and we found that this event revealed an extraordinary complexity of the rupture geometry and evolution: the coseismic rupture propagated almost simultaneously on a normal fault and on a blind fault

  14. Application of random seismic inversion method based on tectonic model in thin sand body research

    Science.gov (United States)

    Dianju, W.; Jianghai, L.; Qingkai, F.

    2017-12-01

    The oil and gas exploitation at Songliao Basin, Northeast China have already progressed to the period with high water production. The previous detailed reservoir description that based on seismic image, sediment core, borehole logging has great limitations in small scale structural interpretation and thin sand body characterization. Thus, precise guidance for petroleum exploration is badly in need of a more advanced method. To do so, we derived the method of random seismic inversion constrained by tectonic model.It can effectively improve the depicting ability of thin sand bodies, combining numerical simulation techniques, which can credibly reducing the blindness of reservoir analysis from the whole to the local and from the macroscopic to the microscopic. At the same time, this can reduce the limitations of the study under the constraints of different geological conditions of the reservoir, accomplish probably the exact estimation for the effective reservoir. Based on the research, this paper has optimized the regional effective reservoir evaluation and the productive location adjustment of applicability, combined with the practical exploration and development in Aonan oil field.

  15. A local adaptive method for the numerical approximation in seismic wave modelling

    Directory of Open Access Journals (Sweden)

    Galuzzi Bruno G.

    2017-12-01

    Full Text Available We propose a new numerical approach for the solution of the 2D acoustic wave equation to model the predicted data in the field of active-source seismic inverse problems. This method consists in using an explicit finite difference technique with an adaptive order of approximation of the spatial derivatives that takes into account the local velocity at the grid nodes. Testing our method to simulate the recorded seismograms in a marine seismic acquisition, we found that the low computational time and the low approximation error of the proposed approach make it suitable in the context of seismic inversion problems.

  16. Seismic facies; Facies sismicas

    Energy Technology Data Exchange (ETDEWEB)

    Johann, Paulo Roberto Schroeder [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao Corporativo. Gerencia de Reservas e Reservatorios]. E-mail: johann@petrobras.com.br

    2004-11-01

    The method presented herein describes the seismic facies as representations of curves and vertical matrixes of the lithotypes proportions. The seismic facies are greatly interested in capturing the spatial distributions (3D) of regionalized variables, as for example, lithotypes, sedimentary facies groups and/ or porosity and/or other properties of the reservoirs and integrate them into the 3D geological modeling (Johann, 1997). Thus when interpreted as curves or vertical matrixes of proportions, seismic facies allow us to build a very important tool for structural analysis of regionalized variables. The matrixes have an important application in geostatistical modeling. In addition, this approach provides results about the depth and scale of the wells profiles, that is, seismic data is integrated to the characterization of reservoirs in depth maps and in high resolution maps. The link between the different necessary technical phases involved in the classification of the segments of seismic traces is described herein in groups of predefined traces of two approaches: a) not supervised and b) supervised by the geological knowledge available on the studied reservoir. The multivariate statistical methods used to obtain the maps of the seismic facies units are interesting tools to be used to provide a lithostratigraphic and petrophysical understanding of a petroleum reservoir. In the case studied these seismic facies units are interpreted as representative of the depositional system as a part of the Namorado Turbiditic System, Namorado Field, Campos Basin.Within the scope of PRAVAP 19 (Programa Estrategico de Recuperacao Avancada de Petroleo - Strategic Program of Advanced Petroleum Recovery) some research work on algorithms is underway to select new optimized attributes to apply seismic facies. One example is the extraction of attributes based on the wavelet transformation and on the time-frequency analysis methodology. PRAVAP is also carrying out research work on an

  17. The imprint of crustal density heterogeneities on regional seismic wave propagation

    NARCIS (Netherlands)

    Plonka, A.I.; Blom, N.A.; Fichtner, A.

    2016-01-01

    Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the

  18. Comparative Application of Capacity Models for Seismic Vulnerability Evaluation of Existing RC Structures

    International Nuclear Information System (INIS)

    Faella, C.; Lima, C.; Martinelli, E.; Nigro, E.

    2008-01-01

    Seismic vulnerability assessment of existing buildings is one of the most common tasks in which Structural Engineers are currently engaged. Since, its is often a preliminary step to approach the issue of how to retrofit non-seismic designed and detailed structures, it plays a key role in the successful choice of the most suitable strengthening technique. In this framework, the basic information for both seismic assessment and retrofitting is related to the formulation of capacity models for structural members. Plenty of proposals, often contradictory under the quantitative standpoint, are currently available within the technical and scientific literature for defining the structural capacity in terms of force and displacements, possibly with reference to different parameters representing the seismic response. The present paper shortly reviews some of the models for capacity of RC members and compare them with reference to two case studies assumed as representative of a wide class of existing buildings

  19. Estimation of Seismic Wavelets Based on the Multivariate Scale Mixture of Gaussians Model

    Directory of Open Access Journals (Sweden)

    Jing-Huai Gao

    2009-12-01

    Full Text Available This paper proposes a new method for estimating seismic wavelets. Suppose a seismic wavelet can be modeled by a formula with three free parameters (scale, frequency and phase. We can transform the estimation of the wavelet into determining these three parameters. The phase of the wavelet is estimated by constant-phase rotation to the seismic signal, while the other two parameters are obtained by the Higher-order Statistics (HOS (fourth-order cumulant matching method. In order to derive the estimator of the Higher-order Statistics (HOS, the multivariate scale mixture of Gaussians (MSMG model is applied to formulating the multivariate joint probability density function (PDF of the seismic signal. By this way, we can represent HOS as a polynomial function of second-order statistics to improve the anti-noise performance and accuracy. In addition, the proposed method can work well for short time series.

  20. Use of a viscoelastic model for the seismic response of base-isolated buildings

    International Nuclear Information System (INIS)

    Uras, R.A.

    1994-01-01

    Due to recent developments in elastomer technology, seismic isolation using elastomer bearings is rapidly becoming an acceptable design tool to enhance structural seismic margins and to protect people and equipment from earthquake damage. With proper design of isolators, high-energy seismic input motions are transformed into low-frequency, low energy harmonic motions and the accelerations acting on the isolated building are significantly reduced. Several alternatives exist for the modeling of the isolators. This study is concerned with the use of a viscoelastic model to predict the seismic response of base-isolated buildings. The in-house finite element computer code has been modified to incorporate a viscoelastic spring element, and several simulations are performed. Then, the computed results have been compared with the corresponding observed data recorded at the test facility

  1. GrowYourIC: an open access Python code to facilitate comparison between kinematic models of inner core evolution and seismic observations

    Science.gov (United States)

    Lasbleis, M.; Day, E. A.; Waszek, L.

    2017-12-01

    The complex nature of inner core structure has been well-established from seismic studies, with heterogeneities at various length scales, both radially and laterally. Despite this, no geodynamic model has successfully explained all of the observed seismic features. To facilitate comparisons between seismic observations and geodynamic models of inner core growth we have developed a new, open access Python tool - GrowYourIC - that allows users to compare models of inner core structure. The code allows users to simulate different evolution models of the inner core, with user-defined rates of inner core growth, translation and rotation. Once the user has "grown" an inner core with their preferred parameters they can then explore the effect of "their" inner core's evolution on the relative age and growth rate in different regions of the inner core. The code will convert these parameters into seismic properties using either built-in mineral physics models, or user-supplied ones that calculate these seismic properties with users' own preferred mineralogical models. The 3D model of isotropic inner core properties can then be used to calculate the predicted seismic travel time anomalies for a random, or user-specified, set of seismic ray paths through the inner core. A real dataset of inner core body-wave differential travel times is included for the purpose of comparing user-generated models of inner core growth to actual observed travel time anomalies in the top 100km of the inner core. Here, we explore some of the possibilities of our code. We investigate the effect of the limited illumination of the inner core by seismic waves on the robustness of kinematic model interpretation. We test the impact on seismic differential travel time observations of several kinematic models of inner core growth: fast lateral translation; slow differential growth; and inner core super-rotation. We find that a model of inner core evolution incorporating both differential growth and slow

  2. The Sacred Mountain of Varallo in Italy: Seismic Risk Assessment by Acoustic Emission and Structural Numerical Models

    Directory of Open Access Journals (Sweden)

    Alberto Carpinteri

    2013-01-01

    Full Text Available We examine an application of Acoustic Emission (AE technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named “The Sacred Mountain of Varallo.” Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular concern due to its uncertain structural condition and due to the level of stress caused by the regional seismicity. Therefore, lifetime assessment, taking into account the evolution of damage phenomena, is necessary to preserve the reliability and safety of this masterpiece of cultural heritage. A continuous AE monitoring was performed to assess the structural behavior of the Chapel. During the monitoring period, a correlation between peaks of AE activity in the masonry of the “Sacred Mountain of Varallo” and regional seismicity was found. Although the two phenomena take place on very different scales, the AE in materials and the earthquakes in Earth’s crust, belong to the same class of invariance. In addition, an accurate finite element model, performed with DIANA finite element code, is presented to describe the dynamic behavior of Chapel XVII structure, confirming visual and instrumental inspections of regional seismic effects.

  3. The Sacred Mountain of Varallo in Italy: seismic risk assessment by acoustic emission and structural numerical models.

    Science.gov (United States)

    Carpinteri, Alberto; Lacidogna, Giuseppe; Invernizzi, Stefano; Accornero, Federico

    2013-01-01

    We examine an application of Acoustic Emission (AE) technique for a probabilistic analysis in time and space of earthquakes, in order to preserve the valuable Italian Renaissance Architectural Complex named "The Sacred Mountain of Varallo." Among the forty-five chapels of the Renaissance Complex, the structure of the Chapel XVII is of particular concern due to its uncertain structural condition and due to the level of stress caused by the regional seismicity. Therefore, lifetime assessment, taking into account the evolution of damage phenomena, is necessary to preserve the reliability and safety of this masterpiece of cultural heritage. A continuous AE monitoring was performed to assess the structural behavior of the Chapel. During the monitoring period, a correlation between peaks of AE activity in the masonry of the "Sacred Mountain of Varallo" and regional seismicity was found. Although the two phenomena take place on very different scales, the AE in materials and the earthquakes in Earth's crust, belong to the same class of invariance. In addition, an accurate finite element model, performed with DIANA finite element code, is presented to describe the dynamic behavior of Chapel XVII structure, confirming visual and instrumental inspections of regional seismic effects.

  4. Finite Element Modelling of Seismic Liquefaction in Soils

    NARCIS (Netherlands)

    Galavi, V.; Petalas, A.; Brinkgreve, R.B.J.

    2013-01-01

    Numerical aspects of seismic liquefaction in soils as implemented in the finite element code, PLAXIS, is described in this paper. After description of finite element equations of dynamic problems, three practical dynamic boundary conditions, namely viscous boundary tractions, tied degrees of freedom

  5. On the modeling and inversion of seismic data

    NARCIS (Netherlands)

    Stolk, C.C.

    2000-01-01

    In this thesis we investigate some mathematical questions related to the inversion of seismic data. In Chapter 2 we review results in the literature and give some new results on wave equations with coefficients that are just bounded and measurable. We show that these equations have unique

  6. The great triangular seismic region in eastern Asia: Thoughts on its dynamic context

    Directory of Open Access Journals (Sweden)

    Xianglin Gao

    2011-01-01

    Full Text Available A huge triangle-shaped tectonic region in eastern Asia plays host to numerous major earthquakes. The three boundaries of this region, which contains plateaus, mountains, and intermountain basins, are roughly the Himalayan arc, the Tianshan-Baikal, and longitude line ∼105°E. Within this triangular region, tectonism is intense and major deformation occurs both between crustal blocks and within most of them. Outside of this region, rigid blocks move as a whole with relatively few major earthquakes and relatively weak Cenozoic deformation. On a large tectonic scale, the presence of this broad region of intraplate deformation results from dynamic interactions between the Indian, Philippine Sea-West Pacific, and Eurasian plates, as well as the influence of deep-level mantle flow. The Indian subcontinent, which continues to move northwards at ∼40 mm/a since its collision with Eurasia, has plunged beneath Tibet, resulting in various movements and deformations along the Himalayan arc that diffuse over a long distance into the hinterland of Asia. The northward crustal escape of Asia from the Himalayan collisional zone turns eastwards and southeastwards along 95°–100°E longitude and defines the eastern Himalayan syntaxis. At the western Himalayan syntaxis, the Pamirs continue to move into central Asia, leading to crustal deformation and earthquakes that are largely accommodated by old EW or NW trending faults in the bordering areas between China, Mongolia, and Russia, and are restricted by the stable landmass northwest of the Tianshan-Altai-Baikal region. The subduction of the Philippine and Pacific plates under the Eurasian continent has generated a very long and narrow seismic zone along trenches and island arcs in the marginal seas while imposing only slight horizontal compression on the Asian continent that does not impede the eastward motion of eastern Asia. In the third dimension, there may be southeastward deep mantle flow beneath most of

  7. Seismic and Thermal Structure of the Arctic Lithosphere, From Waveform Tomography and Thermodynamic Modelling

    Science.gov (United States)

    Lebedev, S.; Schaeffer, A. J.; Fullea, J.; Pease, V.

    2015-12-01

    Thermal structure of the lithosphere is reflected in the values of seismic velocities within it. Our new tomographic models of the crust and upper mantle of the Arctic are constrained by an unprecedentedly large global waveform dataset and provide substantially improved resolution, compared to previous models. The new tomography reveals lateral variations in the temperature and thickness of the lithosphere and defines deep boundaries between tectonic blocks with different lithospheric properties and age. The shape and evolution of the geotherm beneath a tectonic unit depends on both crustal and mantle-lithosphere structure beneath it: the lithospheric thickness and its changes with time (these determine the supply of heat from the deep Earth), the crustal thickness and heat production (the supply of heat from within the crust), and the thickness and thermal conductivity of the sedimentary cover (the insulation). Detailed thermal structure of the basins can be modelled by combining seismic velocities from tomography with data on the crustal structure and heat production, in the framework of computational petrological modelling. The most prominent lateral contrasts across the Arctic are between the cold, thick lithospheres of the cratons (in North America, Greenland and Eurasia) and the warmer, non-cratonic blocks. The lithosphere of the Canada Basin is cold and thick, similar to old oceanic lithosphere elsewhere around the world; its thermal structure offers evidence on its lithospheric age and formation mechanism. At 150-250 km depth, the central Arctic region shows a moderate low-velocity anomaly, cooler than that beneath Iceland and N Atlantic. An extension of N Atlantic low-velocity anomaly into the Arctic through the Fram Strait may indicate an influx of N Atlantic asthenosphere under the currently opening Eurasia Basin.

  8. Modeling the Geometry of Plate Boundary and Seismic Structure in the Southern Ryukyu Trench Subduction Zone, Japan, Using Amphibious Seismic Observations

    Science.gov (United States)

    Yamamoto, Y.; Takahashi, T.; Ishihara, Y.; Kaiho, Y.; Arai, R.; Obana, K.; Nakanishi, A.; Miura, S.; Kodaira, S.; Kaneda, Y.

    2018-02-01

    Here we present the new model, the geometry of the subducted Philippine Sea Plate interface beneath the southern Ryukyu Trench subduction zone, estimated from seismic tomography and focal mechanism estimation by using passive and active data from a temporary amphibious seismic network and permanent land stations. Using relocated low-angle thrust-type earthquakes, repeating earthquakes, and structural information, we constrained the geometry of plate boundary from the trench axis to a 60 km depth with uncertainties of less than 5 km. The estimated plate geometry model exhibited large variation, including a pronounced convex structure that may be evidence of a subducted seamount in the eastern portion of study area, whereas the western part appeared smooth. We also found that the active earthquake region near the plate boundary, defined by the distance from our plate geometry model, was clearly separated from the area dominated by short-term slow-slip events (SSEs). The oceanic crust just beneath the SSE-dominant region, the western part of the study area, showed high Vp/Vs ratios (>1.8), whereas the eastern side showed moderate or low Vp/Vs (<1.75). We interpreted this as an indication that high fluid pressures near the surface of the slab are contributing to the SSE activities. Within the toe of the mantle wedge, P and S wave velocities (<7.5 and <4.2 km/s, respectively) lower than those observed through normal mantle peridotite might suggest that some portions of the mantle may be at least 40% serpentinized.

  9. Seismic waveform inversion best practices: regional, global and exploration test cases

    Science.gov (United States)

    Modrak, Ryan; Tromp, Jeroen

    2016-09-01

    Reaching the global minimum of a waveform misfit function requires careful choices about the nonlinear optimization, preconditioning and regularization methods underlying an inversion. Because waveform inversion problems are susceptible to erratic convergence associated with strong nonlinearity, one or two test cases are not enough to reliably inform such decisions. We identify best practices, instead, using four seismic near-surface problems, one regional problem and two global problems. To make meaningful quantitative comparisons between methods, we carry out hundreds of inversions, varying one aspect of the implementation at a time. Comparing nonlinear optimization algorithms, we find that limited-memory BFGS provides computational savings over nonlinear conjugate gradient methods in a wide range of test cases. Comparing preconditioners, we show that a new diagonal scaling derived from the adjoint of the forward operator provides better performance than two conventional preconditioning schemes. Comparing regularization strategies, we find that projection, convolution, Tikhonov regularization and total variation regularization are effective in different contexts. Besides questions of one strategy or another, reliability and efficiency in waveform inversion depend on close numerical attention and care. Implementation details involving the line search and restart conditions have a strong effect on computational cost, regardless of the chosen nonlinear optimization algorithm.

  10. The effect of regional variation of seismic wave attenuation on the strong ground motion from earthquakes

    Energy Technology Data Exchange (ETDEWEB)

    Chung, D H; Bernreuter, D L

    1981-10-01

    Attenuation is caused by geometric spreading and absorption. Geometric spreading is almost independent of crustal geology and physiographic region, but absorption depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high frequency waves, absorption does not affect ground motion at distances less than about 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States is similar to that in the western United States. Beyond the near field, differences in ground motion can best be accounted for by differences in attenuation caused by differences in absorption. The stress drop of eastern earthquakes may be higher than for western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. But we believe this factor is of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. The characteristics of strong ground motion in the conterminous United States are discussed in light of these considerations, and estimates are made of the epicentral ground motions in the central and eastern United States. (author)

  11. The forearc crustal evolution of Izu-Bonin (Ogasawara) region obtained by seismic reflection and refraction surveys

    Science.gov (United States)

    Yamashita, M.; Kodaira, S.; Takahashi, N.; Tatsumi, Y.; Kaneda, Y.

    2009-12-01

    The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. By previous seismic survey and deep sea drilling, convex basements are distributed along North-South direction in present forearc region. The convex basements are reported to be formed during Oligocene and Eocene (Taylor, 1992). In IBM forearc region, the middle crust with 6 km/s is recognized by seismic survey using OBSs. In IBM region, four IODP drilling sites are proposed in order to understand comprehensive growth process of arc and continental crust evolution. Two of them are located in forearc region. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection survey using 7,800/12,000 cu.in. air gun and 5-6 km streamer with 444/204 ch hydrophones in the IBM region since 2004. We investigate the crustal structure beneath the Izu-Bonin forearc region for contribution of IBM drilling site along five long survey lines, which are across from present volcanic front to forearc basin. Seismic refraction survey is also conducted across forearc region using 84 OBSs every 1 km interval. Shallow crustal structure can be classified four units including basement which compared between previous drilling results and obtained seismic profiles. In IBM forearc region, thick sedimentary basin distribute from east side of volcanic front. Two convex basement peaks are indicated in across profile of forearc region. These peaks are estimated the top of paleoarc (Oligocene and Eocene) by previous ODP drilling. The half graben structure with major displacement is identified from west side of present volcanic front to the top of Oligocene arc. On the other hand, there is no displacement of sediments between the Oligocene arc and Eocene arc. This result shows the same origin of basement between the present volcanic front and Oligocene arc. There is long time difference of

  12. The 2014 update to the National Seismic Hazard Model in California

    Science.gov (United States)

    Powers, Peter; Field, Edward H.

    2015-01-01

    The 2014 update to the U. S. Geological Survey National Seismic Hazard Model in California introduces a new earthquake rate model and new ground motion models (GMMs) that give rise to numerous changes to seismic hazard throughout the state. The updated earthquake rate model is the third version of the Uniform California Earthquake Rupture Forecast (UCERF3), wherein the rates of all ruptures are determined via a self-consistent inverse methodology. This approach accommodates multifault ruptures and reduces the overprediction of moderate earthquake rates exhibited by the previous model (UCERF2). UCERF3 introduces new faults, changes to slip or moment rates on existing faults, and adaptively smoothed gridded seismicity source models, all of which contribute to significant changes in hazard. New GMMs increase ground motion near large strike-slip faults and reduce hazard over dip-slip faults. The addition of very large strike-slip ruptures and decreased reverse fault rupture rates in UCERF3 further enhances these effects.

  13. Selecting ground-motion models developed for induced seismicity in geothermal areas

    Science.gov (United States)

    Edwards, Benjamin; Douglas, John

    2013-11-01

    We present a case study of the ranking and weighting of ground-motion prediction equations (GMPEs) for seismic hazard assessment of enhanced geothermal systems (EGSs). The study region is Cooper Basin (Australia), where a hot-fractured-rock project was established in 2002. We test the applicability of 36 GMPEs based on stochastic simulations previously proposed for use at EGSs. Each GMPE has a set of corresponding model parameters describing stress drop, regional and local (near-surface) attenuation. To select suitable GMPEs for Cooper Basin from the full set, we applied two methods. In the first, seismograms recorded on the local monitoring network were spectrally analysed to determine characteristic stress and attenuation parameters. In a second approach, residual analysis using the log-likelihood (LLH) method was used to directly compare recorded and predicted short-period response spectral accelerations. The resulting ranking was consistent with the models selected based on spectral analysis, with the advantage that a transparent weighting approach was available using the LLH method. Region-specific estimates of variability were computed, with significantly lower values observed compared to previous studies of small earthquakes. This was consistent with the limited range of stress drops and attenuation observed from the spectral analysis.

  14. Optimization of Regional Geodynamic Models for Mantle Dynamics

    Science.gov (United States)

    Knepley, M.; Isaac, T.; Jadamec, M. A.

    2016-12-01

    The SubductionGenerator program is used to construct high resolution, 3D regional thermal structures for mantle convection simulations using a variety of data sources, including sea floor ages and geographically referenced 3D slab locations based on seismic observations. The initial bulk temperature field is constructed using a half-space cooling model or plate cooling model, and related smoothing functions based on a diffusion length-scale analysis. In this work, we seek to improve the 3D thermal model and test different model geometries and dynamically driven flow fields using constraints from observed seismic velocities and plate motions. Through a formal adjoint analysis, we construct the primal-dual version of the multi-objective PDE-constrained optimization problem for the plate motions and seismic misfit. We have efficient, scalable preconditioners for both the forward and adjoint problems based upon a block preconditioning strategy, and a simple gradient update is used to improve the control residual. The full optimal control problem is formulated on a nested hierarchy of grids, allowing a nonlinear multigrid method to accelerate the solution.

  15. Application of mass-spring model in seismic analysis of liquid storage tank

    International Nuclear Information System (INIS)

    Liu Jiayi; Bai Xinran; Li Xiaoxuan

    2013-01-01

    There are many tanks for storing liquid in nuclear power plant. When seismic analysis is performed, swaying of liquid may change the mechanical parameters of those tanks, such as the center of mass and the moment of inertia, etc., so the load due to swaying of liquid can't be neglected. Mass-spring model is a simplified model to calculate the dynamic pressure of liquid in tank under earthquake, which is derived by the theory of Housner and given in the specification of seismic analysis of Safety-Related Nuclear Structures and Commentary-4-98 (ASCE-4-98 for short hereinafter). According to the theory of Housner and ASCE-4-98, the mass-spring 3-D FEM model for storage tank and liquid in it was established, by which the force of stored liquid acted on liquid storage tank in nuclear power plant under horizontal seismic load was calculated. The calculated frequency of liquid swaying and effect of liquid convection on storage tank were compared with those calculated by simplified formula. It is shown that the results of 3-D FEM model are reasonable and reliable. Further more, it is more direct and convenient compared with description in ASCE-4-98 when the mass-spring model is applied to 3-D FEM model for seismic analysis, from which the displacement and stress distributions of the plate-shell elements or the 3-D solid finite elements can be obtained directly from the seismic input model. (authors)

  16. Analysis of seismic reflectivity and AVO pattern of BSR using OBS data in the southwestern offshore region of Taiwan

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, W.B.; Yang, H.R. [Jinwen Univ. of Science and Technology, Hsintien City, Taipei County, Taiwan (China). Dept. of Environment and Property Management; Schnurle, P.; Liu, C.S. [National Taiwan Univ., Taipei, Taiwan (China). Inst. of Oceanography; Lee, C.S. [National Taiwan Ocean Univ., Keelung, Taiwan (China). Inst. of Applied Earth Science; Wang, Y.; Chung, S.H.; Chen, S.C. [Ministry of Economic Affairs, Taiwan (China). Central Geological Survey

    2008-07-01

    Regional multi-channel seismic reflection profiles that were conducted in Taiwan from 2003 to 2006 resulted in the identification of a gas hydrate-related bottom simulating reflector (BSR) in the broad southwestern offshore region of Taiwan. In order to understand the regional distribution of methane hydrate bearing layers and explore concentrated hydrate bearing layers, this paper presented a comprehensive analysis of reflection coefficient and amplitude-versus-offset (AVO) pattern of BSR using ocean bottom seismographs (OBSs) seismic data acquired in the southwestern offshore region of Taiwan. The study focused on the analysis and interpretation of airgun array signals recorded by OBSs during 2004 and 2006. Ten profiles of seismic reflection/refraction with a total length of about 140 km and recorded by 50 recovered OBSs were acquired on the active and passive margins in offshore southwestern Taiwan. Amplitudes of the direct water arrival, the multiple, and the BSR were picked interactively for all the OBS lines. A quantitative representation of reflector strength was provided by calculation of reflection coefficients. In general, the seafloor reflection coefficients for the active and passive margins were estimated as 0.1-0.25. The paper presented the data and analysis as well as the results of the study. It was concluded that the results of calculated reflection coefficient of the BSR in offshore southwest Taiwan suggested that inferred hydrate concentration for the passive margin profiles was relatively higher than that for the active margin profiles. 4 refs.

  17. A GIS-based time-dependent seismic source modeling of Northern Iran

    Science.gov (United States)

    Hashemi, Mahdi; Alesheikh, Ali Asghar; Zolfaghari, Mohammad Reza

    2017-01-01

    The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran.

  18. Nature of the uppermost mantle below the Porcupine Basin, offshore Ireland: new insights from seismic refraction and gravity data modeling

    Science.gov (United States)

    Prada, M.; Watremez, L.; Chen, C.; O'Reilly, B.; Minshull, T. A.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

    2015-12-01

    The Porcupine Basin is a tongue-shaped basin SW of Ireland formed during the opening of the North Atlantic Ocean. Its history of sedimentation reveals several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on seismic and gravity data, suggest the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Serpentinization is a key factor in lithospheric extension since it reduces the strength of mantle rocks, and hence, influences the tectonics of the lithosphere. Besides reducing the seismic velocity of the rock, serpentinization decreases mantle rock density favoring isostatic rebound and basin uplift, thus affecting the tectonic and thermal evolution of the basin. Here we characterize the deep structure of the Porcupine Basin from wide-angle seismic (WAS) and gravity data, with especial emphasis on the nature of the underlying mantle. The WAS data used were acquired along a 300 km long transect across the northern region of the basin. We used a travel time inversion method to model the data and obtain a P-wave velocity (Vp) model of the crust and uppermost mantle, together with the geometry of the main geological interfaces. The crustal structure along the model reveals a maximum stretching factor of ~5-6. These values are well within the range of crustal extension at which the crust becomes entirely brittle allowing the formation of major crustal faulting and serpentinization of the mantle. To further constrain the seismic structure and hence the nature of the mantle we assess the Vp uncertainty of the model by means of a Monte Carlo analysis and perform gravity modeling to test different interpretations regarding mantle rock nature. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  19. Seismic zonation of Bucharest by using a deterministic approach of numerical modeling

    International Nuclear Information System (INIS)

    Moldoveanu, C.L.; Panza, G.F.; Cioflan, C.; Radulian, M.; Marmureanu, Gh.

    2002-01-01

    Bucharest city represents the largest European center (about 2 million inhabitants and 230 km 2 constructed area) periodically subjected to the strong intermediate-depth earthquakes originating in Vrancea region. The statistics indicate a recurrence interval of 25 years for M w ≥7.0 Vrancea events and a significant earthquake hazard for the city location with a 50% chance for an event of M w >7.6 every 50 years. The strongest Vrancea events of the last century occurred in 1908 (M w =7.1), 1940 (M w =7.7), 1977 (M w =7.4) and 1986 (M w =7.1) and inflicted heavy damage and casualties in Bucharest. Under these circumstances, the ground motion evaluation for the city area represents an essential step toward the mitigation of the local seismic risk. This paper presents the new insights coming from direct instrumental observation and interpretation of the local effects as well as realistic numerical modeling that update and improve the input data necessary for a detailed microzoning map of the Romanian capital. Our results show that the synthetic local hazard distribution we obtain with the deterministic approach supplies a realistic estimation of the seismic input, highly sensitive not only to the local conditions, but also to the source and the path structure parameters. The complex hybrid method we use offers the chance to merge the different specific accumulated information in reasonably well constrained scenarios for a level C realistic microzonation of Bucharest area to be use to mitigate the effects of future strong events originating in Vrancea region. (authors)

  20. Seismic attenuation relationship with homogeneous and heterogeneous prediction-error variance models

    Science.gov (United States)

    Mu, He-Qing; Xu, Rong-Rong; Yuen, Ka-Veng

    2014-03-01

    Peak ground acceleration (PGA) estimation is an important task in earthquake engineering practice. One of the most well-known models is the Boore-Joyner-Fumal formula, which estimates the PGA using the moment magnitude, the site-to-fault distance and the site foundation properties. In the present study, the complexity for this formula and the homogeneity assumption for the prediction-error variance are investigated and an efficiency-robustness balanced formula is proposed. For this purpose, a reduced-order Monte Carlo simulation algorithm for Bayesian model class selection is presented to obtain the most suitable predictive formula and prediction-error model for the seismic attenuation relationship. In this approach, each model class (a predictive formula with a prediction-error model) is evaluated according to its plausibility given the data. The one with the highest plausibility is robust since it possesses the optimal balance between the data fitting capability and the sensitivity to noise. A database of strong ground motion records in the Tangshan region of China is obtained from the China Earthquake Data Center for the analysis. The optimal predictive formula is proposed based on this database. It is shown that the proposed formula with heterogeneous prediction-error variance is much simpler than the attenuation model suggested by Boore, Joyner and Fumal (1993).

  1. New Frontiers on Seismic Modeling of Masonry Structures

    Directory of Open Access Journals (Sweden)

    Salvatore Caddemi

    2017-07-01

    Full Text Available An accurate evaluation of the non-linear behavior of masonry structural elements in existing buildings still represents a complex issue that rigorously requires non-linear finite element strategies difficult to apply to real large structures. Nevertheless, for the static and seismic assessment of existing structures, involving the contribution of masonry materials, engineers need reliable and efficient numerical tools, whose complexity and computational demand should be suitable for practical purposes. For these reasons, the formulation and the validation of simplified numerical strategies represent a very important issue in masonry computational research. In this paper, an innovative macroelement approach, developed by the authors in the last decade, is presented. The proposed macroelement formulation is based on different, plane and spatial, macroelements for the simulation of both the in-plane and out-of-plane behavior of masonry structures also in presence of masonry elements with curved geometry. The mechanical response of the adopted macroelement is governed by non-linear zero-thickness interfaces, whose calibration follows a straightforward fiber discretization, and the non-linear internal shear deformability is ruled by equivalence with a corresponding geometrically consistent homogenized medium. The approach can be considered as “parsimonious” since the kinematics of the adopted elements is controlled by very few degrees of freedom, if compared to a corresponding discretization performed by using non-linear finite element method strategies. This innovative discrete element strategy has been implemented in two user-oriented software codes 3DMacro (Caliò et al., 2012b and HiStrA (Historical Structures Analysis (Caliò et al., 2015, which simplify the modeling of buildings and historical structures by means of several wizard generation tools and input/output facilities. The proposed approach, that represents a powerful tool for the

  2. Structure of the Koyna-Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

    Science.gov (United States)

    Catchings, Rufus D.; Dixit, M.M.; Goldman, Mark R.; Kumar, S.

    2015-01-01

    The Koyna-Warna area of India is one of the best worldwide examples of reservoir-induced seismicity, with the distinction of having generated the largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, the fault structure and tectonic setting that has accommodated the induced seismicity is poorly known, in part because the seismic events occur beneath a thick sequence of basalt layers. On the basis of the alignment of earthquake epicenters over an ~50 year period, lateral variations in focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, and magnetotelluric), geomorphic data, and correlation with similar structures elsewhere, we suggest that the Koyna-Warna area lies within a right step between northwest trending, right-lateral faults. The sub-basalt basement may form a local structural depression (pull-apart basin) caused by extension within the step-over zone between the right-lateral faults. Our postulated model accounts for the observed pattern of normal faulting in a region that is dominated by north-south directed compression. The right-lateral faults extend well beyond the immediate Koyna-Warna area, possibly suggesting a more extensive zone of seismic hazards for the central India area. Induced seismic events have been observed many places worldwide, but relatively large-magnitude induced events are less common because critically stressed, preexisting structures are a necessary component. We suggest that releasing bends and fault step-overs like those we postulate for the Koyna-Warna area may serve as an ideal tectonic environment for generating moderate- to large- magnitude induced (reservoir, injection, etc.) earthquakes.

  3. Study of Site Effect at Seismic Station Located in Undermined Area of Karviná Region (Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Lednická, Markéta; Kaláb, Zdeněk

    2016-01-01

    Roč. 64, č. 5 (2016), s. 1715-1730 ISSN 1895-7455 R&D Projects: GA ČR GP13-07027P Institutional support: RVO:68145535 Keywords : Karviná region * site effect * SSR * HVSR * mining induced seismicity Subject RIV: JM - Building Engineering Impact factor: 0.968, year: 2016 http://agp.igf.edu.pl/files/64/5/Lednicka-Kalab.pdf

  4. Body and Surface Wave Modeling of Observed Seismic Events

    Science.gov (United States)

    1981-04-30

    mechanisms for foreshock , mainshock, and aftershock sequences using Seismic Research Observatory (SRO) data, EOS, 57(12), p. 954, 1976. Bache, T.C., W.L...the event as well as that of the immediate foreshock were 95 located (Allen and Nordquist, 1972) and where the largest surface displacements were...1972). Foreshock , main shock and larger aftershocks of the Borrego Mountain earthquake, U. S. Geological Survey Professional Paper 787, 16-23. Bache

  5. Exploring the Gross Schoenebeck (Germany) geothermal site using a statistical joint interpretation of magnetotelluric and seismic tomography models

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, Gerard; Bauer, Klaus; Moeck, Inga; Schulze, Albrecht; Ritter, Oliver [Deutsches GeoForschungsZentrum (GFZ), Telegrafenberg, 14473 Potsdam (Germany)

    2010-03-15

    Exploration for geothermal resources is often challenging because there are no geophysical techniques that provide direct images of the parameters of interest, such as porosity, permeability and fluid content. Magnetotelluric (MT) and seismic tomography methods yield information about subsurface distribution of resistivity and seismic velocity on similar scales and resolution. The lack of a fundamental law linking the two parameters, however, has limited joint interpretation to a qualitative analysis. By using a statistical approach in which the resistivity and velocity models are investigated in the joint parameter space, we are able to identify regions of high correlation and map these classes (or structures) back onto the spatial domain. This technique, applied to a seismic tomography-MT profile in the area of the Gross Schoenebeck geothermal site, allows us to identify a number of classes in accordance with the local geology. In particular, a high-velocity, low-resistivity class is interpreted as related to areas with thinner layers of evaporites; regions where these sedimentary layers are highly fractured may be of higher permeability. (author)

  6. Tomographic models and seismotectonics of the Reggio Emilia region, Italy

    Science.gov (United States)

    Ciaccio, M. G.; Chiarabba, C.

    2002-02-01

    The aim of this study is to define the Vp and Vp/Vs structure of the fault zone ruptured by the M L 5.1 earthquake of October 15, 1996 which occurred near Reggio Emilia (central-northern Italy). A 1-month-long seismic sequence followed the mainshock and occurred in a small region along the outer border of the northern Apenninic belt, at depth ranging between 10 and 17 km. P- and S-wave arrival times from 304 aftershocks recorded by two local dense seismic arrays installed in the epicentral region have been inverted to obtain one- and three-dimensional velocity models by using state of the art local earthquake tomographic techniques. Velocity models and aftershock relocation help us to infer the seismotectonic of the region. Earthquakes originated along a NW-dipping backthrust of a NE-trending main thrust, composing the western part of the broad Ferrara Arc. A main high Vp and high Vp/Vs region delineates a pop-up structure in the center of the area. The high Vp/Vs within the pop-up structure supports the presence of a zone with increased pore pressure. The hypocentral depth of both mainshock and aftershocks is greater than those usually found for the main seismogenic regions of the Apenninic belt. P-wave velocity values in the seismogenic area, obtained by tomography, are compatible with rocks of the Mesozoic cover and suggest that seismicity occurred within the Mesozoic units stack at present by compressional tectonics.

  7. Shear-wave velocity models and seismic sources in Campanian volcanic areas: Vesuvius and Phlegraean fields

    Energy Technology Data Exchange (ETDEWEB)

    Guidarelli, M; Zille, A; Sarao, A [Dipartimento di Scienze della Terra, Universita degli Studi di Trieste, Trieste (Italy); Natale, M; Nunziata, C [Dipartimento di Geofisica e Vulcanologia, Universita di Napoli ' Federico II' , Napoli (Italy); Panza, G F [Dipartimento di Scienze della Terra, Universita degli Studi di Trieste, Trieste (Italy); Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)

    2006-12-15

    This chapter summarizes a comparative study of shear-wave velocity models and seismic sources in the Campanian volcanic areas of Vesuvius and Phlegraean Fields. These velocity models were obtained through the nonlinear inversion of surface-wave tomography data, using as a priori constraints the relevant information available in the literature. Local group velocity data were obtained by means of the frequency-time analysis for the time period between 0.3 and 2 s and were combined with the group velocity data for the time period between 10 and 35 s from the regional events located in the Italian peninsula and bordering areas and two station phase velocity data corresponding to the time period between 25 and 100 s. In order to invert Rayleigh wave dispersion curves, we applied the nonlinear inversion method called hedgehog and retrieved average models for the first 30-35 km of the lithosphere, with the lower part of the upper mantle being kept fixed on the basis of existing regional models. A feature that is common to the two volcanic areas is a low shear velocity layer which is centered at the depth of about 10 km, while on the outside of the cone and along a path in the northeastern part of the Vesuvius area this layer is absent. This low velocity can be associated with the presence of partial melting and, therefore, may represent a quite diffused crustal magma reservoir which is fed by a deeper one that is regional in character and located in the uppermost mantle. The study of seismic source in terms of the moment tensor is suitable for an investigation of physical processes within a volcano; indeed, its components, double couple, compensated linear vector dipole, and volumetric, can be related to the movements of magma and fluids within the volcanic system. Although for many recent earthquake events the percentage of double couple component is high, our results also show the presence of significant non-double couple components in both volcanic areas. (author)

  8. Long-term seismicity of the Reykjanes Ridge (North Atlantic) recorded by a regional hydrophone array

    Science.gov (United States)

    Goslin, Jean; Lourenço, Nuno; Dziak, Robert P.; Bohnenstiehl, DelWayne R.; Haxel, Joe; Luis, Joaquim

    2005-08-01

    The seismicity of the northern Mid-Atlantic Ridge was recorded by two hydrophone networks moored in the sound fixing and ranging (SOFAR) channel, on the flanks of the Mid-Atlantic Ridge, north and south of the Azores. During its period of operation (05/2002-09/2003), the northern `SIRENA' network, deployed between latitudes 40° 20'N and 50° 30'N, recorded acoustic signals generated by 809 earthquakes on the hotspot-influenced Reykjanes Ridge. This activity was distributed between five spatio-temporal event clusters, each initiated by a moderate-to-large magnitude (4.0-5.6 M) earthquake. The rate of earthquake occurrence within the initial portion of the largest sequence (which began on 2002 October 6) is described adequately by a modified Omori law aftershock model. Although this is consistent with triggering by tectonic processes, none of the Reykjanes Ridge sequences are dominated by a single large-magnitude earthquake, and they appear to be of relatively short duration (0.35-4.5 d) when compared to previously described mid-ocean ridge aftershock sequences. The occurrence of several near-equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of mainshock-induced stresses and may reflect the involvement of magmatic or fluid processes along this deep (>2000 m) section of the Reykjanes Ridge.

  9. The finite-difference and finite-element modeling of seismic wave propagation and earthquake motion

    International Nuclear Information System (INIS)

    Moszo, P.; Kristek, J.; Galis, M.; Pazak, P.; Balazovijech, M.

    2006-01-01

    Numerical modeling of seismic wave propagation and earthquake motion is an irreplaceable tool in investigation of the Earth's structure, processes in the Earth, and particularly earthquake phenomena. Among various numerical methods, the finite-difference method is the dominant method in the modeling of earthquake motion. Moreover, it is becoming more important in the seismic exploration and structural modeling. At the same time we are convinced that the best time of the finite-difference method in seismology is in the future. This monograph provides tutorial and detailed introduction to the application of the finite-difference, finite-element, and hybrid finite-difference-finite-element methods to the modeling of seismic wave propagation and earthquake motion. The text does not cover all topics and aspects of the methods. We focus on those to which we have contributed. (Author)

  10. Three-dimensional cellular automata as a model of a seismic fault

    International Nuclear Information System (INIS)

    Gálvez, G; Muñoz, A

    2017-01-01

    The Earth's crust is broken into a series of plates, whose borders are the seismic fault lines and it is where most of the earthquakes occur. This plating system can in principle be described by a set of nonlinear coupled equations describing the motion of the plates, its stresses, strains and other characteristics. Such a system of equations is very difficult to solve, and nonlinear parts leads to a chaotic behavior, which is not predictable. In 1989, Bak and Tang presented an earthquake model based on the sand pile cellular automata. The model though simple, provides similar results to those observed in actual earthquakes. In this work the cellular automata in three dimensions is proposed as a best model to approximate a seismic fault. It is noted that the three-dimensional model reproduces similar properties to those observed in real seismicity, especially, the Gutenberg-Richter law. (paper)

  11. Time-lapse seismic waveform modelling and attribute analysis using hydromechanical models for a deep reservoir undergoing depletion

    Science.gov (United States)

    He, Y.-X.; Angus, D. A.; Blanchard, T. D.; Wang, G.-L.; Yuan, S.-Y.; Garcia, A.

    2016-04-01

    Extraction of fluids from subsurface reservoirs induces changes in pore pressure, leading not only to geomechanical changes, but also perturbations in seismic velocities and hence observable seismic attributes. Time-lapse seismic analysis can be used to estimate changes in subsurface hydromechanical properties and thus act as a monitoring tool for geological reservoirs. The ability to observe and quantify changes in fluid, stress and strain using seismic techniques has important implications for monitoring risk not only for petroleum applications but also for geological storage of CO2 and nuclear waste scenarios. In this paper, we integrate hydromechanical simulation results with rock physics models and full-waveform seismic modelling to assess time-lapse seismic attribute resolution for dynamic reservoir characterization and hydromechanical model calibration. The time-lapse seismic simulations use a dynamic elastic reservoir model based on a North Sea deep reservoir undergoing large pressure changes. The time-lapse seismic traveltime shifts and time strains calculated from the modelled and processed synthetic data sets (i.e. pre-stack and post-stack data) are in a reasonable agreement with the true earth models, indicating the feasibility of using 1-D strain rock physics transform and time-lapse seismic processing methodology. Estimated vertical traveltime shifts for the overburden and the majority of the reservoir are within ±1 ms of the true earth model values, indicating that the time-lapse technique is sufficiently accurate for predicting overburden velocity changes and hence geomechanical effects. Characterization of deeper structure below the overburden becomes less accurate, where more advanced time-lapse seismic processing and migration is needed to handle the complex geometry and strong lateral induced velocity changes. Nevertheless, both migrated full-offset pre-stack and near-offset post-stack data image the general features of both the overburden and

  12. A Comparison of Moment Rates for the Eastern Mediterranean Region from Competitive Kinematic Models

    Science.gov (United States)

    Klein, E. C.; Ozeren, M. S.; Shen-Tu, B.; Galgana, G. A.

    2017-12-01

    Relatively continuous, complex, and long-lived episodes of tectonic deformation gradually shaped the lithosphere of the eastern Mediterranean region into its present state. This large geodynamically interconnected and seismically active region absorbs, accumulates and transmits strains arising from stresses associated with: (1) steady northward convergence of the Arabian and African plates; (2) differences in lithospheric gravitational potential energy; and (3) basal tractions exerted by subduction along the Hellenic and Cyprus Arcs. Over the last twenty years, numerous kinematic models have been built using a variety of assumptions to take advantage of the extensive and dense GPS observations made across the entire region resulting in a far better characterization of the neotectonic deformation field than ever previously achieved. In this study, three separate horizontal strain rate field solutions obtained from three, region-wide, GPS only based kinematic models (i.e., a regional block model, a regional continuum model, and global continuum model) are utilized to estimate the distribution and uncertainty of geodetic moment rates within the eastern Mediterranean region. The geodetic moment rates from each model are also compared with seismic moment release rates gleaned from historic earthquake data. Moreover, kinematic styles of deformation derived from each of the modeled horizontal strain rate fields are examined for their degree of correlation with earthquake rupture styles defined by proximal centroid moment tensor solutions. This study suggests that significant differences in geodetically obtained moment rates from competitive kinematic models may introduce unforeseen bias into regularly updated, geodetically constrained, regional seismic hazard assessments.

  13. Structure and Deformation in the Transpressive Zone of Southern California Inferred from Seismicity, Velocity, and Qp Models

    Science.gov (United States)

    Hauksson, E.; Shearer, P.

    2004-12-01

    We synthesize relocated regional seismicity and 3D velocity and Qp models to infer structure and deformation in the transpressive zone of southern California. These models provide a comprehensive synthesis of the tectonic fabric of the upper to middle crust, and the brittle ductile transition zone that in some cases extends into the lower crust. The regional seismicity patterns in southern California are brought into focus when the hypocenters are relocated using the double difference method. In detail, often the spatial correlation between background seismicity and late Quaternary faults is improved as the hypocenters become more clustered, and the spatial patterns are more sharply defined. Along some of the strike-slip faults the seismicity clusters decrease in width and form alignments implying that in many cases the clusters are associated with a single fault. In contrast, the Los Angeles Basin seismicity remains mostly scattered, reflecting a 3D distribution of the tectonic compression. We present the results of relocating 327,000 southern California earthquakes that occurred between 1984 and 2002. In particular, the depth distribution is improved and less affected by layer boundaries in velocity models or other similar artifacts, and thus improves the definition of the brittle ductile transition zone. The 3D VP and VP/VS models confirm existing tectonic interpretations and provide new insights into the configuration of the geological structures in southern California. The models extend from the US-Mexico border in the south to the Coast Ranges and Sierra Nevada in the north, and have 15 km horizontal grid spacing and an average vertical grid spacing of 4 km, down to 22 km depth. The heterogeneity of the crustal structure as imaged in both the VP and VP/VS models is larger within the Pacific than the North America plate, reflecting regional asymmetric variations in the crustal composition and past tectonic processes. Similarly, the relocated seismicity is

  14. CyberShake: A Physics-Based Seismic Hazard Model for Southern California

    Science.gov (United States)

    Graves, R.; Jordan, T.H.; Callaghan, S.; Deelman, E.; Field, E.; Juve, G.; Kesselman, C.; Maechling, P.; Mehta, G.; Milner, K.; Okaya, D.; Small, P.; Vahi, K.

    2011-01-01

    CyberShake, as part of the Southern California Earthquake Center's (SCEC) Community Modeling Environment, is developing a methodology that explicitly incorporates deterministic source and wave propagation effects within seismic hazard calculations through the use of physics-based 3D ground motion simulations. To calculate a waveform-based seismic hazard estimate for a site of interest, we begin with Uniform California Earthquake Rupture Forecast, Version 2.0 (UCERF2.0) and identify all ruptures within 200 km of the site of interest. We convert the UCERF2.0 rupture definition into multiple rupture variations with differing hypocenter locations and slip distributions, resulting in about 415,000 rupture variations per site. Strain Green Tensors are calculated for the site of interest using the SCEC Community Velocity Model, Version 4 (CVM4), and then, using reciprocity, we calculate synthetic seismograms for each rupture variation. Peak intensity measures are then extracted from these synthetics and combined with the original rupture probabilities to produce probabilistic seismic hazard curves for the site. Being explicitly site-based, CyberShake directly samples the ground motion variability at that site over many earthquake cycles (i. e., rupture scenarios) and alleviates the need for the ergodic assumption that is implicitly included in traditional empirically based calculations. Thus far, we have simulated ruptures at over 200 sites in the Los Angeles region for ground shaking periods of 2 s and longer, providing the basis for the first generation CyberShake hazard maps. Our results indicate that the combination of rupture directivity and basin response effects can lead to an increase in the hazard level for some sites, relative to that given by a conventional Ground Motion Prediction Equation (GMPE). Additionally, and perhaps more importantly, we find that the physics-based hazard results are much more sensitive to the assumed magnitude-area relations and

  15. Aseismic and seismic slip induced by fluid injection from poroelastic and rate-state friction modeling

    Science.gov (United States)

    Liu, Y.; Deng, K.; Harrington, R. M.; Clerc, F.

    2016-12-01

    Solid matrix stress change and pore pressure diffusion caused by fluid injection has been postulated as key factors for inducing earthquakes and aseismic slip on pre-existing faults. In this study, we have developed a numerical model that simulates aseismic and seismic slip in a rate-and-state friction framework with poroelastic stress perturbations from multi-stage hydraulic fracturing scenarios. We apply the physics-based model to the 2013-2015 earthquake sequences near Fox Creek, Alberta, Canada, where three magnitude 4.5 earthquakes were potentially induced by nearby hydraulic fracturing activity. In particular, we use the relocated December 2013 seismicity sequence to approximate the fault orientation, and find the seismicity migration spatiotemporally correlate with the positive Coulomb stress changes calculated from the poroelastic model. When the poroelastic stress changes are introduced to the rate-state friction model, we find that slip on the fault evolves from aseismic to seismic in a manner similar to the onset of seismicity. For a 15-stage hydraulic fracturing that lasted for 10 days, modeled fault slip rate starts to accelerate after 3 days of fracking, and rapidly develops into a seismic event, which also temporally coincides with the onset of induced seismicity. The poroelastic stress perturbation and consequently fault slip rate continue to evolve and remain high for several weeks after hydraulic fracturing has stopped, which may explain the continued seismicity after shut-in. In a comparison numerical experiment, fault slip rate quickly decreases to the interseismic level when stress perturbations are instantaneously returned to zero at shut-in. Furthermore, when stress perturbations are removed just a few hours after the fault slip rate starts to accelerate (that is, hydraulic fracturing is shut down prematurely), only aseismic slip is observed in the model. Our preliminary results thus suggest the design of fracturing duration and flow

  16. 3-D crustal P-wave velocity tomography of the Italian region using local and regional seismicity data

    Directory of Open Access Journals (Sweden)

    F. M. Mele

    1995-06-01

    Full Text Available A tomographic experiment was performed in the Italian region using local and regional arrivaI times of p and S seismological phases selected from the Italian National Bulletin in the time interval 1984-1991. We deter- mined a 3-D crustal P-wave velocity model using a simultaneous inversion method that iteratively re1ocates the hypocenters and computes the unknown model parameters. A fast two-point ray tracing algorithm was adopted to compute the ray paths and travel times of P", S", P g' Sg phases with good accuracy. Synthetic tests were performed using the "true" hypocenter and station distribution to rough1y evaluate the extension of the areas most densely spanned by the ray paths; the agreement between synthetic and computed models is more satisfactory at Moho depths than in the upper crust. The qua1ity of the model resulting from inversion of real data is examined by the ca1culation of the Spread Function (Toomey and Foulger, 1989. The 3-D crustal P-wave velocity mode1 of the Italian region shows remarkab1e trends at Moho depths: the areas east of the Apennines call for positive adjustments of the initial velocity va1ue, while the west region shows negative ad- justments. The correspondence among the main features of the velocity field, the map of Moho isobaths and the map of the gravity anoma1ies is also outlined.

  17. Implementation of NGA-West2 ground motion models in the 2014 U.S. National Seismic Hazard Maps

    Science.gov (United States)

    Rezaeian, Sanaz; Petersen, Mark D.; Moschetti, Morgan P.; Powers, Peter; Harmsen, Stephen C.; Frankel, Arthur D.

    2014-01-01

    The U.S. National Seismic Hazard Maps (NSHMs) have been an important component of seismic design regulations in the United States for the past several decades. These maps present earthquake ground shaking intensities at specified probabilities of being exceeded over a 50-year time period. The previous version of the NSHMs was developed in 2008; during 2012 and 2013, scientists at the U.S. Geological Survey have been updating the maps based on their assessment of the “best available science,” resulting in the 2014 NSHMs. The update includes modifications to the seismic source models and the ground motion models (GMMs) for sites across the conterminous United States. This paper focuses on updates in the Western United States (WUS) due to the use of new GMMs for shallow crustal earthquakes in active tectonic regions developed by the Next Generation Attenuation (NGA-West2) project. Individual GMMs, their weighted combination, and their impact on the hazard maps relative to 2008 are discussed. In general, the combined effects of lower medians and increased standard deviations in the new GMMs have caused only small changes, within 5–20%, in the probabilistic ground motions for most sites across the WUS compared to the 2008 NSHMs.

  18. Seismic tests on models of reinforced-concrete Category I buildings

    International Nuclear Information System (INIS)

    Dove, R.C.; Endebrock, E.G.; Dunwoody, W.E.; Bennett, J.G.

    1985-01-01

    The behavior of reinforced concrete (R/C), Category I noncontainment nuclear power plant structures subjected to seismic events of magnitude greater than used in their original design has been investigated using two sizes of scale models. Test results were analyzed to determine (1) maximum input for the response to remain linear/elastic; (2) changes in stiffness, damping, and modal frequency that are produced by seismic input greater than that causing linear elastic response; (3) changes in floor response spectra when the structure's response is nonlinear/inelastic; and (4) the magnitude of the seismic event necessary to fail (excessively crack) these structures. By constructing models of two sizes, it was possible to make two independent predictions of prototype behavior and to compare the results from the two models. 1 ref., 4 figs., 1 tab

  19. Construction of the seismic wave-speed model by adjoint tomography beneath the Japanese metropolitan area

    Science.gov (United States)

    Miyoshi, Takayuki

    2017-04-01

    The Japanese metropolitan area has high risks of earthquakes and volcanoes associated with convergent tectonic plates. It is important to clarify detail three-dimensional structure for understanding tectonics and predicting strong motion. Classical tomographic studies based on ray theory have revealed seismotectonics and volcanic tectonics in the region, however it is unknown whether their models reproduce observed seismograms. In the present study, we construct new seismic wave-speed model by using waveform inversion. Adjoint tomography and the spectral element method (SEM) were used in the inversion (e.g. Tape et al. 2009; Peter et al. 2011). We used broadband seismograms obtained at NIED F-net stations for 140 earthquakes occurred beneath the Kanto district. We selected four frequency bands between 5 and 30 sec and used from the seismograms of longer period bands for the inversion. Tomographic iteration was conducted until obtaining the minimized misfit between data and synthetics. Our SEM model has 16 million grid points that covers the metropolitan area of the Kanto district. The model parameters were the Vp and Vs of the grid points, and density and attenuation were updated to new values depending on new Vs in each iteration. The initial model was assumed the tomographic model (Matsubara and Obara 2011) based on ray theory. The source parameters were basically used from F-net catalog, while the centroid times were inferred from comparison between data and synthetics. We simulated the forward and adjoint wavefields of each event and obtained Vp and Vs misfit kernels from their interaction. Large computation was conducted on K computer, RIKEN. We obtained final model (m16) after 16 iterations in the present study. For the waveform improvement, it is clearly shown that m16 is better than the initial model, and the seismograms especially improved in the frequency bands of longer than 8 sec and changed better for seismograms of the events occurred at deeper than a

  20. Homogenised constitutive model dedicated to reinforced concrete plates subjected to seismic solicitations

    International Nuclear Information System (INIS)

    Combescure, Christelle

    2013-01-01

    Safety reassessments are periodically performed on the EDF nuclear power plants and the recent seismic reassessments leaded to the necessity of taking into account the non-linear behaviour of materials when modeling and simulating industrial structures of these power plants under seismic solicitations. A large proportion of these infrastructures is composed of reinforced concrete buildings, including reinforced concrete slabs and walls, and literature seems to be poor on plate modeling dedicated to seismic applications for this material. As for the few existing models dedicated to these specific applications, they present either a lack of dissipation energy in the material behaviour, or no micromechanical approach that justifies the parameters needed to properly describe the model. In order to provide a constitutive model which better represents the reinforced concrete plate behaviour under seismic loadings and whose parameters are easier to identify for the civil engineer, a constitutive model dedicated to reinforced concrete plates under seismic solicitations is proposed: the DHRC (Dissipative Homogenised Reinforced Concrete) model. Justified by a periodic homogenisation approach, this model includes two dissipative phenomena: damage of concrete matrix and internal sliding at the interface between steel rebar and surrounding concrete. An original coupling term between damage and sliding, resulting from the homogenisation process, induces a better representation of energy dissipation during the material degradation. The model parameters are identified from the geometric characteristics of the plate and a restricted number of material characteristics, allowing a very simple use of the model. Numerical validations of the DHRC model are presented, showing good agreement with experimental behaviour. A one dimensional simplification of the DHRC model is proposed, allowing the representation of reinforced concrete bars and simplified models of rods and wire mesh

  1. Predictability in the Epidemic-Type Aftershock Sequence model of interacting triggered seismicity

    Science.gov (United States)

    Helmstetter, AgnèS.; Sornette, Didier

    2003-10-01

    As part of an effort to develop a systematic methodology for earthquake forecasting, we use a simple model of seismicity on the basis of interacting events which may trigger a cascade of earthquakes, known as the Epidemic-Type Aftershock Sequence model (ETAS). The ETAS model is constructed on a bare (unrenormalized) Omori law, the Gutenberg-Richter law, and the idea that large events trigger more numerous aftershocks. For simplicity, we do not use the information on the spatial location of earthquakes and work only in the time domain. We demonstrate the essential role played by the cascade of triggered seismicity in controlling the rate of aftershock decay as well as the overall level of seismicity in the presence of a constant external seismicity source. We offer an analytical approach to account for the yet unobserved triggered seismicity adapted to the problem of forecasting future seismic rates at varying horizons from the present. Tests presented on synthetic catalogs validate strongly the importance of taking into account all the cascades of still unobserved triggered events in order to predict correctly the future level of seismicity beyond a few minutes. We find a strong predictability if one accepts to predict only a small fraction of the large-magnitude targets. Specifically, we find a prediction gain (defined as the ratio of the fraction of predicted events over the fraction of time in alarms) equal to 21 for a fraction of alarm of 1%, a target magnitude M ≥ 6, an update time of 0.5 days between two predictions, and for realistic parameters of the ETAS model. However, the probability gains degrade fast when one attempts to predict a larger fraction of the targets. This is because a significant fraction of events remain uncorrelated from past seismicity. This delineates the fundamental limits underlying forecasting skills, stemming from an intrinsic stochastic component in these interacting triggered seismicity models. Quantitatively, the fundamental

  2. THMC Modeling of EGS Reservoirs -- Continuum through Discontinuum Representations. Capturing Reservoir Stimulation, Evolution and Induced Seismicity

    Energy Technology Data Exchange (ETDEWEB)

    Elsworth, Derek [Pennsylvania State Univ., State College, PA (United States); Izadi, Ghazal [Pennsylvania State Univ., State College, PA (United States); Gan, Quan [Pennsylvania State Univ., State College, PA (United States); Fang, Yi [Pennsylvania State Univ., State College, PA (United States); Taron, Josh [US Geological Survey, Menlo Park, CA (United States); Sonnenthal, Eric [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-07-28

    This work has investigated the roles of effective stress induced by changes in fluid pressure, temperature and chemistry in contributing to the evolution of permeability and induced seismicity in geothermal reservoirs. This work has developed continuum models [1] to represent the progress or seismicity during both stimulation [2] and production [3]. These methods have been used to resolve anomalous observations of induced seismicity at the Newberry Volcano demonstration project [4] through the application of modeling and experimentation. Later work then focuses on the occurrence of late stage seismicity induced by thermal stresses [5] including the codifying of the timing and severity of such responses [6]. Furthermore, mechanistic linkages between observed seismicity and the evolution of permeability have been developed using data from the Newberry project [7] and benchmarked against field injection experiments. Finally, discontinuum models [8] incorporating the roles of discrete fracture networks have been applied to represent stimulation and then thermal recovery for new arrangements of geothermal wells incorporating the development of flow manifolds [9] in order to increase thermal output and longevity in EGS systems.

  3. Velocity Model Analysis Based on Integrated Well and Seismic Data of East Java Basin

    Science.gov (United States)

    Mubin, Fathul; Widya, Aviandy; Eka Nurcahya, Budi; Nurul Mahmudah, Erma; Purwaman, Indro; Radityo, Aryo; Shirly, Agung; Nurwani, Citra

    2018-03-01

    Time to depth conversion is an important processof seismic interpretationtoidentify hydrocarbonprospectivity. Main objectives of this research are to minimize the risk of error in geometry and time to depth conversion. Since it’s using a large amount of data and had been doing in the large scale of research areas, this research can be classified as a regional scale research. The research was focused on three horizons time interpretation: Top Kujung I, Top Ngimbang and Basement which located in the offshore and onshore areas of east Java basin. These three horizons was selected because they were assumed to be equivalent to the rock formation, which is it has always been the main objective of oil and gas exploration in the East Java Basin. As additional value, there was no previous works on velocity modeling for regional scale using geological parameters in East Java basin. Lithology and interval thickness were identified as geological factors that effected the velocity distribution in East Java Basin. Therefore, a three layer geological model was generated, which was defined by the type of lithology; carbonate (layer 1: Top Kujung I), shale (layer 2: Top Ngimbang) and Basement. A statistical method using three horizons is able to predict the velocity distribution on sparse well data in a regional scale. The average velocity range for Top Kujung I is 400 m/s - 6000 m/s, Top Ngimbang is 500 m/s - 8200 m/s and Basement is 600 m/s - 8000 m/s. Some velocity anomalies found in Madura sub-basin area, caused by geological factor which identified as thick shale deposit and high density values on shale. Result of velocity and depth modeling analysis can be used to define the volume range deterministically and to make geological models to prospect generation in details by geological concept.

  4. How a joint interpretation of seismic scattering, velocity, and attenuation models explains the nature of the Campi Flegrei (Italy).

    Science.gov (United States)

    Calo, M.; Tramelli, A.

    2017-12-01

    Seismic P and S velocity models (and their ratio Vp/Vs) help illuminating the geometrical structure of the bodies and give insight on the presence of water, molten or gas saturated regions. Seismic attenuation represents the anelastic behavior of the medium. Due to its dependence on temperature, fluid contents and cracks presence, this parameter is also largely used to characterize the structures of volcanoes and geothermal areas. Scattering attenuation is related, in the upper crust, to the amount, size and organization of the fractures giving complementary information on the state of the medium.Therefore a joint interpretation of these models provides an exhaustive view of the elastic parameters in volcanic regions. Campi Flegrei is an active Caldera marked by strong vertical deformations of the ground called bradyseisms and several models have been proposed to describe the nature and the geometry of the bodies responsible of the bradyseisms. Here we show Vp, Vp/Vs, Qp and scattering models carried out by applying an enhanced seismic tomography method that combines de double difference approach (Zhang and Thurber, 2003) and the Weigthed Average Method (Calò et al., 2009, Calò et al., 2011, 2013). The data used are the earthquakes recorded during the largest bradyseism crisis of the 80's. Our method allowed to image structures with linear dimension of 0.5-1.2km, resulting in an improvement of the resolving power at least two times of the other published models (e.g. Priolo et al., 2012). The joint interpretation of seismic models allowed to discern small anomalous bodies at shallow depth (0.5-2.0 km) marked by relatively low Vp, high Vp/Vs ratio and low Qp values associated with the presence of shallow geothermal water saturated reservoir from regions with low Vp, low Vp/Vs and low Qp related to the gas saturated part of the reservoir. At deeper depth (2-3.5 km) bodies with high Vp and Vp/Vs and low Qp are associated with magmatic intrusions. The Scattering

  5. An integrated geodetic and seismic study of the Cusco Fault system in the Cusco Region-Southern Peru

    Science.gov (United States)

    Norabuena, E. O.; Tavera, H. J.

    2017-12-01

    The Cusco Fault system is composed by six main faults (Zurite, Tamboray, Qoricocha, Tambomachay, Pachatusan, and Urcos) extending in a NW-SE direction over the Cusco Region in southeastern Peru. From these, the Tambomachay is a normal fault of 20 km length, strikes N120°E and bounds a basin filled with quaternary lacustrine and fluvial deposits. Given its 5 km distance to Cusco, an historical and Inca's archeological landmark, it represents a great seismic hazard for its more than 350,000 inhabitants. The Tambomachay fault as well as the other secondary faults have been a source of significant seismic activity since historical times being the more damaging ones the Cusco earthquakes of 1650, 1950 and more recently April 1986 (M 5.8). Previous geological studies indicate that at the beginning of the Quaternary the fault showed a transcurrent mechanism leading to the formation of the Cusco basin. However, nowadays its mechanism is normal fault and scarps up to 22m can be observed. We report the current dynamics of the Tambomachay fault and secondary faults based on seismic activity imaged by a network of 29 broadband stations deployed in the Cusco Region as well as the deformation field inferred from GPS survey measurements carried out between 2014 and 2016.

  6. Viscoplastic discontinuum model of time-dependent fracture and seismicity effects in brittle rock

    CSIR Research Space (South Africa)

    Napier, JAL

    1997-10-01

    Full Text Available A model is proposed for the direct mechanistic simulation of seismic activity and stress transfer effects in deep level mines. The model uses a discontinuum viscoplastic formulation to relate the rate of slip on a crack to the shear stress acting...

  7. Determination of the 8° discontinuity beneath the major tectonic units of Central Europe from regional seismicity in Europe and northern Africa

    Science.gov (United States)

    Nita, B.; Perchuc, E.; Thybo, H.; Maguire, P.; Denton, P.

    2004-12-01

    We evaluate the existence and the depth of the '8° discontinuity' beneath the Alpine orogen using the natural seismicity of Europe and northern Africa as well as events induced by mining activity. For this analysis, the regional events (1) must have epicenters further than 1000 km from the structure being imaged, and (2) the magnitude of body waves must be higher than 4.0 to obtain a favourable signal to noise ratio. The events satisfying the above conditions have epicentres in Algeria, Spain, Bulgaria, Greece and in the Lubin Copper Basin in Poland. The last region is characterised by high seismicity resulting from mining activity. We base our analysis on P-wave traveltime residuals compared to the general iasp91 model. The 8° discontinuity seems to be attributed to the observed P-wave traveltime delays at epicentral distances around 800 km. The analysis of events from the Lubin Coper Basin and the events from other regions mentioned above, gives P-wave delays of 3 s at the Alpine stations in comparison with stations in the Variscan areas to further north. We attribute this variation in travel time to the difference between 'fast' and 'slow' uppermost mantle structures in Europe.

  8. Monte Carlo Analysis of Reservoir Models Using Seismic Data and Geostatistical Models

    Science.gov (United States)

    Zunino, A.; Mosegaard, K.; Lange, K.; Melnikova, Y.; Hansen, T. M.

    2013-12-01

    We present a study on the analysis of petroleum reservoir models consistent with seismic data and geostatistical constraints performed on a synthetic reservoir model. Our aim is to invert directly for structure and rock bulk properties of the target reservoir zone. To infer the rock facies, porosity and oil saturation seismology alone is not sufficient but a rock physics model must be taken into account, which links the unknown properties to the elastic parameters. We then combine a rock physics model with a simple convolutional approach for seismic waves to invert the "measured" seismograms. To solve this inverse problem, we employ a Markov chain Monte Carlo (MCMC) method, because it offers the possibility to handle non-linearity, complex and multi-step forward models and provides realistic estimates of uncertainties. However, for large data sets the MCMC method may be impractical because of a very high computational demand. To face this challenge one strategy is to feed the algorithm with realistic models, hence relying on proper prior information. To address this problem, we utilize an algorithm drawn from geostatistics to generate geologically plausible models which represent samples of the prior distribution. The geostatistical algorithm learns the multiple-point statistics from prototype models (in the form of training images), then generates thousands of different models which are accepted or rejected by a Metropolis sampler. To further reduce the computation time we parallelize the software and run it on multi-core machines. The solution of the inverse problem is then represented by a collection of reservoir models in terms of facies, porosity and oil saturation, which constitute samples of the posterior distribution. We are finally able to produce probability maps of the properties we are interested in by performing statistical analysis on the collection of solutions.

  9. Using Seismic Interferometry to Investigate Seismic Swarms

    Science.gov (United States)

    Matzel, E.; Morency, C.; Templeton, D. C.

    2017-12-01

    Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

  10. Necessity of using heterogeneous ellipsoidal Earth model with terrain to calculate co-seismic effect

    Science.gov (United States)

    Cheng, Huihong; Zhang, Bei; Zhang, Huai; Huang, Luyuan; Qu, Wulin; Shi, Yaolin

    2016-04-01

    Co-seismic deformation and stress changes, which reflect the elasticity of the earth, are very important in the earthquake dynamics, and also to other issues, such as the evaluation of the seismic risk, fracture process and triggering of earthquake. Lots of scholars have researched the dislocation theory and co-seismic deformation and obtained the half-space homogeneous model, half-space stratified model, spherical stratified model, and so on. Especially, models of Okada (1992) and Wang (2003, 2006) are widely applied in the research of calculating co-seismic and post-seismic effects. However, since both semi-infinite space model and layered model do not take the role of the earth curvature or heterogeneity or topography into consideration, there are large errors in calculating the co-seismic displacement of a great earthquake in its impacted area. Meanwhile, the computational methods of calculating the co-seismic strain and stress are different between spherical model and plane model. Here, we adopted the finite element method which could well deal with the complex characteristics (such as anisotropy, discontinuities) of rock and different conditions. We use the mash adaptive technique to automatically encrypt the mesh at the fault and adopt the equivalent volume force replace the dislocation source, which can avoid the difficulty in handling discontinuity surface with conventional (Zhang et al., 2015). We constructed an earth model that included earth's layered structure and curvature, the upper boundary was set as a free surface and the core-mantle boundary was set under buoyancy forces. Firstly, based on the precision requirement, we take a testing model - - a strike-slip fault (the length of fault is 500km and the width is 50km, and the slippage is 10m) for example. Because of the curvature of the Earth, some errors certainly occur in plane coordinates just as previous studies (Dong et al., 2014; Sun et al., 2012). However, we also found that: 1) the co-seismic

  11. Seismic Structure of Southern African Cratons

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Artemieva, Irina; Levander, Alan

    2014-01-01

    functions and finite-frequency tomography based on data from the South Africa Seismic Experiment (SASE). Combining the two methods provides high vertical and lateral resolution. The main results obtained are (1) the presence of a highly heterogeneous crustal structure, in terms of thickness, composition (as......Cratons are extremely stable continental crustal areas above thick depleted lithosphere. These regions have remained largely unchanged for more than 2.5 Ga. This study presents a new seismic model of the seismic structure of the crust and lithospheric mantle constrained by seismic receiver...

  12. Complex structure of the lithospheric slab beneath the Banda arc, eastern Indonesia depicted by a seismic tomographic model

    Directory of Open Access Journals (Sweden)

    Sri Widiyantoro

    2011-10-01

    Full Text Available Seismic tomography with a non-linear approach has been successfully applied to image the P-wave velocity structure beneath the Banda arc in detail. Nearly one million compressional phases including the surfacereflected depth phases pP and pwP from events within the Indonesian region have been used. The depth phases have been incorporated in order to improve the sampling of the uppermantle structure, particularly below the Banda Sea in the back-arc regions. For the model parameterization, we have combined a highresolution regional inversion with a low-resolution global inversion to allow detailed images of slab structures within the study region and to minimize the mapping of distant aspherical mantle structure into the volume under study. In this paper, we focus our discussion on the upper mantle and transition zone structure beneath the curved Banda arc. The tomographic images confirm previous observations of the twisting of the slab in the upper mantle, forming a spoon-shaped structure beneath the Banda arc. A slab lying flat on the 660 km discontinuity beneath the Banda Sea is also well imaged. Further interpretations of the resulting tomograms and seismicity data support the scenario of the Banda arc subduction rollback.

  13. NEESROCK: A Physical and Numerical Modeling Investigation of Seismically Induced Rock-Slope Failure

    Science.gov (United States)

    Applegate, K. N.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Adams, S.; Arnold, L.; Gibson, M.; Smith, S.

    2013-12-01

    Worldwide, seismically induced rock-slope failures have been responsible for approximately 30% of the most significant landslide catastrophes of the past century. They are among the most common, dangerous, and still today, least understood of all seismic hazards. Seismically Induced Rock-Slope Failure: Mechanisms and Prediction (NEESROCK) is a major research initiative that fully integrates physical modeling (geotechnical centrifuge) and advanced numerical simulations (discrete element modeling) to investigate the fundamental mechanisms governing the stability of rock slopes during earthquakes. The research is part of the National Science Foundation-supported Network for Earthquake Engineering Simulation Research (NEES) program. With its focus on fractures and rock materials, the project represents a significant departure from the traditional use of the geotechnical centrifuge for studying soil, and pushes the boundaries of physical modeling in new directions. In addition to advancing the fundamental understanding of the rock-slope failure process under seismic conditions, the project is developing improved rock-slope failure assessment guidelines, analysis procedures, and predictive tools. Here, we provide an overview of the project, present experimental and numerical modeling results, discuss special considerations for the use of synthetic rock materials in physical modeling, and address the suitability of discrete element modeling for simulating the dynamic rock-slope failure process.

  14. Ground Motion Prediction Models for Caucasus Region

    Science.gov (United States)

    Jorjiashvili, Nato; Godoladze, Tea; Tvaradze, Nino; Tumanova, Nino

    2016-04-01

    Ground motion prediction models (GMPMs) relate ground motion intensity measures to variables describing earthquake source, path, and site effects. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration or spectral acceleration because this parameter gives useful information for Seismic Hazard Assessment. Since 2003 development of Georgian Digital Seismic Network has started. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models is obtained by classical, statistical way, regression analysis. In this study site ground conditions are additionally considered because the same earthquake recorded at the same distance may cause different damage according to ground conditions. Empirical ground-motion prediction models (GMPMs) require adjustment to make them appropriate for site-specific scenarios. However, the process of making such adjustments remains a challenge. This work presents a holistic framework for the development of a peak ground acceleration (PGA) or spectral acceleration (SA) GMPE that is easily adjustable to different seismological conditions and does not suffer from the practical problems associated with adjustments in the response spectral domain.

  15. Investigation of the seismicity at regional and teleseismic distances following underground nuclear detonations. Final technical report

    International Nuclear Information System (INIS)

    Willis, D.E.; Stubenrauch, A.; Willis, M.E.

    1977-01-01

    The main emphasis of the investigation was to determine the seismicity of the Nevada Test Site area during a time period which encompassed a lull in the testing program. The time period studied extends from April 1, 1973 to October 1, 1975. The aftershock sequence of nuclear shots fired on Pahute Mesa during late 1975 and early 1976 were also included

  16. Refinement of Regional Distance Seismic Moment Tensor and Uncertainty Analysis for Source-Type Identification

    Science.gov (United States)

    2014-09-02

    also present an application of a continuous scanning method to small events recorded locally. The events are associated with the evolution of a sinkhole ...triangles), approximate location of Oxy Geismar 3 cavern (white square) and an average point location of the sinkhole (white balloon...events of the Louisiana sinkhole seismic sequence.................................................................................49 Figure 31. (a

  17. Seismic hazard assessment for Central, North and Northwest Europe: GSHAP Region 3

    Czech Academy of Sciences Publication Activity Database

    Grunthal, G.; Bosse, Ch.; Camelbeeck, T.; de Crook, T.; Gariel, J. C.; Gregersen, S.; Guterch, B.; Halldorsson, P.; Labák, P.; Lindholm, C.; Lenhardt, W.; Mantyniemi, P.; Mayer-Rosa, D.; Musson, R. M. W.; Schenk, Vladimír; Schenková, Zdeňka; Slejko, D.; Verbeiren, R.; Wahlstrom, R.; Zabukovec, B.; Ziros, T.

    1999-01-01

    Roč. 42, č. 6 (1999), s. 999-1011 ISSN 0365-2556 R&D Projects: GA AV ČR Global Seismic Hazard Assessment Program (GSHAP) - project of the UN International Decade of Natural Disaster Reduction and International Litosphere Program. Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  18. Seismicity of the Tihamat-Asir region, Kingdom of Saudi Arabia

    Science.gov (United States)

    Merghelani, Habib M.

    1979-01-01

    Knowledge of the seismicity of the west coast of Saudi Arabia is vitally important to the Kingdom. The eastern margin of the Red Sea, which includes all of the west coast of Saudi Arabia, is possibly cut by transform faults that may be capable of producing earthquakes large enough to cause damage in the heavily populated areas or in the industrial complexes under construction. Prior to this study, there were no seismic stations in Saudi Arabia and no studies of microearthquake activity. It was generally assumed that there were no active faults along the west coast. During the period 20 January to 22 February, 1978, five portable seismic stations were deployed in the Tihamat Asir in the southwest part of the country. A significant level of microearthquake activity was detected at a location that approximately coincides with the landward extension of the proposed transform fault. The recording of these earthquakes demonstrates that there are active faults at this location, probably associated with the currently active Red Sea tectonic system. The practical significance of these earthquakes cannot be evaluated from the few data available, and further studies should be undertaken to determine if there are significant seismic hazards along the west coast of Saudi Arabia. 

  19. Regional Characteristics of Stress State of Main Seismic Active Faults in Mid-Northern Part of Sichuan-Yunnan Block

    Science.gov (United States)

    Weiwei, W.; Yaling, W.

    2017-12-01

    We restore the seismic source spectrums of 1012 earthquakes(2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block(26 ° N-33 ° N, 99 ° E-104 ° E),then calculate the source parameters.Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units (Z1 Jinshajiang and Litang fault zone, Z2 Xianshuihe fault zone, Z3 Anninghe-Zemuhe fault zone, Z4 Lijiang-Xiaojinhe fault zone). Seismic source stress drop results show the following, (1)The stress at the end of the Jinshajiang fault is low, strong earthquake activity rare.Stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2)Stress drop of Z2 is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garzê-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3)High stress-drop events were concentrated on Z3, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4)On Z4, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply.The study also show that, (1)Stress drops display a systematic change with different faults and locations, high stress-drop events occurs mostly on the fault intersection area. Faults without locking condition and mainly creep, are mainly characterized by low stress drop. (2)Contrasting to what is commonly thought that "strike-slip faults are not easy to accumulate stress ", Z2 and Z3 all exhibit high stress levels, which

  20. The influence of regional geological settings on the seismic hazard level in copper mines in the Legnica-Głogów Copper Belt Area (Poland

    Directory of Open Access Journals (Sweden)

    Burtan Zbigniew

    2017-01-01

    Full Text Available The current level of rockburst hazard in copper mines of the (LGOM Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

  1. The influence of regional geological settings on the seismic hazard level in copper mines in the Legnica-Głogów Copper Belt Area (Poland)

    Science.gov (United States)

    Burtan, Zbigniew

    2017-11-01

    The current level of rockburst hazard in copper mines of the (LGOM) Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

  2. Seismic assessment of Kozloduy VVER 440, Model 230 nuclear power plant

    International Nuclear Information System (INIS)

    Monette, P.; Baltus, R.; Yanev, P.; Campbell, R.

    1991-01-01

    Excluding system design deficiency relative to US and Western Europe standards, it was found that the plant has many seismic vulnerabilities similar to those that existed in many of the US plants prior to about 1979 when the Systematic Evaluation Program was initiated. The primary coolant system has been substantially upgraded after the 1977 Vrancea earthquake. Other upgrades have been made to weak elements in the ECCS and electrical systems. There are still a number of components that could likely survive the currently defined Safe Shutdown Earthquake of 0.1 g but which would not meet current design standards. Many of the weakest components could be upgraded at a moderate cost to withstand a seismic event exceeding 0.1 g. Current studies of the site seismicity lean toward a higher peak ground acceleration and increased amplification of building motion, thus backfits that have been accomplished may become marginal for newly defined loads. However the proper consideration of soil structure interaction and detailed structural analysis using less conservative modeling assumptions, could mitigate the impact of increasing the seismic input and limit the amount of reinforcement required. In the interim, substantial improvements to seismic safety could be accomplished by simple, inexpensive modifications to equipment anchorage and some achievable improvements to connection detail of the precast concrete structures. (author)

  3. Seismic moment tensor inversion using 3D velocity model and its application to the 2013 Lushan earthquake sequence

    Science.gov (United States)

    Zhu, Lupei; Zhou, Xiaofeng

    2016-10-01

    Source inversion of small-magnitude events such as aftershocks or mine collapses requires use of relatively high frequency seismic waveforms which are strongly affected by small-scale heterogeneities in the crust. In this study, we developed a new inversion method called gCAP3D for determining general moment tensor of a seismic source using Green's functions of 3D models. It inherits the advantageous features of the ;Cut-and-Paste; (CAP) method to break a full seismogram into the Pnl and surface-wave segments and to allow time shift between observed and predicted waveforms. It uses grid search for 5 source parameters (relative strengths of the isotropic and compensated-linear-vector-dipole components and the strike, dip, and rake of the double-couple component) that minimize the waveform misfit. The scalar moment is estimated using the ratio of L2 norms of the data and synthetics. Focal depth can also be determined by repeating the inversion at different depths. We applied gCAP3D to the 2013 Ms 7.0 Lushan earthquake and its aftershocks using a 3D crustal-upper mantle velocity model derived from ambient noise tomography in the region. We first relocated the events using the double-difference method. We then used the finite-differences method and reciprocity principle to calculate Green's functions of the 3D model for 20 permanent broadband seismic stations within 200 km from the source region. We obtained moment tensors of the mainshock and 74 aftershocks ranging from Mw 5.2 to 3.4. The results show that the Lushan earthquake is a reverse faulting at a depth of 13-15 km on a plane dipping 40-47° to N46° W. Most of the aftershocks occurred off the main rupture plane and have similar focal mechanisms to the mainshock's, except in the proximity of the mainshock where the aftershocks' focal mechanisms display some variations.

  4. Study on vertical seismic response model of BWR-type reactor building

    International Nuclear Information System (INIS)

    Konno, T.; Motohashi, S.; Izumi, M.; Iizuka, S.

    1993-01-01

    A study on advanced seismic design for LWR has been carried out by the Nuclear Power Engineering Corporation (NUPEC), under the sponsorship of the Ministry of International Trade and Industry (MITI) of Japan. As a part of the study, it has been investigated to construct an accurate analytical model of reactor buildings for a seismic response analysis, which can reasonably represent dynamic characteristics of the building. In Japan, vibration models of reactor buildings for horizontal ground motion have been studied and examined through many simulation analyses for forced vibration tests and earthquake observations of actual buildings. And now it is possible to establish a reliable horizontal vibration model on the basis of multi-lumped mass and spring model. However, vertical vibration models have not been so much studied as horizontal models, due to less observed data for vertical motions. In this paper, the vertical seismic response models of a BWR-type reactor building including soil-structure interaction effect are numerically studied, by comparing the dynamic characteristics of (1) three dimensional finite element model, (2) multi-stick lumped mass model with a flexible base-mat, (3) multi-stick lumped mass model with a rigid base-mat and (4) single-stick lumped mass model. In particular, the BWR-type reactor building has the long span truss roof which is considered to be one of the critical members to vertical excitation. The modelings of the roof trusses are also studied

  5. Active and fossil mantle flows in the western Alpine region unravelled by seismic anisotropy analysis and high-resolution P wave tomography

    Science.gov (United States)

    Salimbeni, Simone; Malusà, Marco G.; Zhao, Liang; Guillot, Stéphane; Pondrelli, Silvia; Margheriti, Lucia; Paul, Anne; Solarino, Stefano; Aubert, Coralie; Dumont, Thierry; Schwartz, Stéphane; Wang, Qingchen; Xu, Xiaobing; Zheng, Tianyu; Zhu, Rixiang

    2018-04-01

    The anisotropy of seismic velocities in the mantle, when integrated with high-resolution tomographic models and geologic information, can be used to detect active mantle flows in complex plate boundary areas, providing new insights on the impact of mantle processes on the topography of mountain belts. Here we use a densely spaced array of temporary broadband seismic stations to analyze the seismic anisotropy pattern of the western Alpine region, at the boundary between the Alpine and Apenninic slabs. Our results are supportive of a polyphase development of anisotropic mantle fabrics, possibly starting from the Jurassic to present. Geophysical data presented in this work, and geologic evidence taken from the literature, indicate that: (i) fossil fabrics formed during Tethyan rifting may be still preserved within the Alpine and Apenninic slabs; (ii) mantle deformation during Apenninic slab rollback is not compensated by a complete toroidal flow around the northern tip of the retreating slab; (iii) the previously observed continuous trend of anisotropy fast axes near-parallel to the western Alpine arc is confirmed. We observe that this arc-parallel trend of fast axes is located in correspondence to a low velocity anomaly in the European upper mantle, beneath regions of the Western and Ligurian Alps showing the highest uplift rates. We propose that the progressive rollback of the Apenninic slab, in the absence of a counterclockwise toroidal flow at its northern tip, induced a suction effect at the scale of the supraslab mantle. The resulting mantle flow pattern was characterized by an asthenospheric counterflow at the rear of the unbroken Western Alps slab and around its southern tip, and by an asthenospheric upwelling, mirrored by low P wave velocities, that would have favored the topographic uplift of the Alpine belt from the Mont Blanc to the Mediterranean sea.

  6. The Effects of Realistic Geological Heterogeneity on Seismic Modeling: Applications in Shear Wave Generation and Near-Surface Tunnel Detection

    Science.gov (United States)

    Sherman, Christopher Scott

    Naturally occurring geologic heterogeneity is an important, but often overlooked, aspect of seismic wave propagation. This dissertation presents a strategy for modeling the effects of heterogeneity using a combination of geostatistics and Finite Difference simulation. In the first chapter, I discuss my motivations for studying geologic heterogeneity and seis- mic wave propagation. Models based upon fractal statistics are powerful tools in geophysics for modeling heterogeneity. The important features of these fractal models are illustrated using borehole log data from an oil well and geomorphological observations from a site in Death Valley, California. A large part of the computational work presented in this disserta- tion was completed using the Finite Difference Code E3D. I discuss the Python-based user interface for E3D and the computational strategies for working with heterogeneous models developed over the course of this research. The second chapter explores a phenomenon observed for wave propagation in heteroge- neous media - the generation of unexpected shear wave phases in the near-source region. In spite of their popularity amongst seismic researchers, approximate methods for modeling wave propagation in these media, such as the Born and Rytov methods or Radiative Trans- fer Theory, are incapable of explaining these shear waves. This is primarily due to these method's assumptions regarding the coupling of near-source terms with the heterogeneities and mode conversion. To determine the source of these shear waves, I generate a suite of 3D synthetic heterogeneous fractal geologic models and use E3D to simulate the wave propaga- tion for a vertical point force on the surface of the models. I also present a methodology for calculating the effective source radiation patterns from the models. The numerical results show that, due to a combination of mode conversion and coupling with near-source hetero- geneity, shear wave energy on the order of 10% of the

  7. Beam model for seismic analysis of complex shear wall structure based on the strain energy equivalence

    International Nuclear Information System (INIS)

    Reddy, G.R.; Mahajan, S.C.; Suzuki, Kohei

    1997-01-01

    A nuclear reactor building structure consists of shear walls with complex geometry, beams and columns. The complexity of the structure is explained in the section Introduction. Seismic analysis of the complex reactor building structure using the continuum mechanics approach may produce good results but this method is very difficult to apply. Hence, the finite element approach is found to be an useful technique for solving the dynamic equations of the reactor building structure. In this approach, the model which uses finite elements such as brick, plate and shell elements may produce accurate results. However, this model also poses some difficulties which are explained in the section Modeling Techniques. Therefore, seismic analysis of complex structures is generally carried out using a lumped mass beam model. This model is preferred because of its simplicity and economy. Nevertheless, mathematical modeling of a shear wall structure as a beam requires specialized skill and a thorough understanding of the structure. For accurate seismic analysis, it is necessary to model more realistically the stiffness, mass and damping. In linear seismic analysis, modeling of the mass and damping may pose few problems compared to modeling the stiffness. When used to represent a complex structure, the stiffness of the beam is directly related to the shear wall section properties such as area, shear area and moment of inertia. Various beam models which are classified based on the method of stiffness evaluation are also explained under the section Modeling Techniques. In the section Case Studies the accuracy and simplicity of the beam models are explained. Among various beam models, the one which evaluates the stiffness using strain energy equivalence proves to be the simplest and most accurate method for modeling the complex shear wall structure. (author)

  8. Combined rock-physical modelling and seismic inversion techniques for characterisation of stacked sandstone reservoir

    NARCIS (Netherlands)

    Justiniano, A.; Jaya, Y.; Diephuis, G.; Veenhof, R.; Pringle, T.

    2015-01-01

    The objective of the study is to characterise the Triassic massive stacked sandstone deposits of the Main Buntsandstein Subgroup at Block Q16 located in the West Netherlands Basin. The characterisation was carried out through combining rock-physics modelling and seismic inversion techniques. The

  9. Results from an acoustic modelling study of seismic airgun survey noise in Queen Charlotte Basin

    Energy Technology Data Exchange (ETDEWEB)

    MacGillivray, A.O.; Chapman, N.R. [Victoria Univ., BC (Canada). School of Earth and Ocean Sciences

    2005-12-07

    An acoustic modelling study was conducted to examine seismic survey noise propagation in the Queen Charlotte Basin (QCB) and better understand the physical aspects of sound transmission. The study results are intended to help determine the potential physiological and behavioural effects of airgun noise on marine mammals and fish. The scope of the study included a numerical simulation of underwater sound transmission in QCB in areas where oil and gas exploration activities may be conducted; a forecast of received noise levels by combining acoustic transmission loss computations with acoustic source levels representative of seismic exploration activity and, the use of received forecasts to estimate zones of impact for marine mammals. The critical environmental parameters in the QCB are the bathymetry of the ocean, the sound speed profile in the water and the geoacoustic profile of the seabed. The RAM acoustic propagation model developed by the United States Naval Research Laboratory was used to compute acoustic transmission loss in the QCB. The source level and directionality of the seismic array was determined by a full-waveform array source signature model. This modelling study of noise propagation from seismic surveys revealed several key findings. Among them, it showed that received noise levels in the water are affected by the source location, array orientation and the shape of the sound speed profile with respect to water depth. It also showed that noise levels are lowest in shallow bathymetry. 30 refs., 5 tabs., 13 figs.

  10. co-seismic grace gravity based 11-layered 3-d thrust fault model for ...

    Indian Academy of Sciences (India)

    30

    It honours co-seismic deformation of ocean surface, ocean ... has caused great damage (Sumatra earthquake 2004 Wikipedia) when the Indian Plate ..... Gokula, A P, Sastry R G (2015a) Gravitational attraction of a vertical pyramid model of flat ... Journal. 14, 1-21. Lay T, Kanamori H, Ammon CJ, Nettles M, Ward SN, Aster ...

  11. Model Based Beamforming and Bayesian Inversion Signal Processing Methods for Seismic Localization of Underground Source

    DEFF Research Database (Denmark)

    Oh, Geok Lian

    properties such as the elastic wave speeds and soil densities. One processing method is casting the estimation problem into an inverse problem to solve for the unknown material parameters. The forward model for the seismic signals used in the literatures include ray tracing methods that consider only...... density values of the discretized ground medium, which leads to time-consuming computations and instability behaviour of the inversion process. In addition, the geophysics inverse problem is generally ill-posed due to non-exact forward model that introduces errors. The Bayesian inversion method through...... the first arrivals of the reflected compressional P-waves from the subsurface structures, or 3D elastic wave models that model all the seismic wave components. The ray tracing forward model formulation is linear, whereas the full 3D elastic wave model leads to a nonlinear inversion problem. In this Ph...

  12. Sunda-Banda Arc Transition: Marine Wide-Angle Seismic Modeling

    Science.gov (United States)

    Shulgin, A.; Planert, L.; Kopp, H.; Mueller, C.; Lueschen, E.; Engels, M.; Flueh, E.; Djajadihardja, Y.; Sindbad Working Group, T

    2008-12-01

    The Sunda-Banda Arc transition is the region of active convergence and collision of the Indo-Australian and Eurasian Plates. The style of subduction changes from an oceanic-island arc subduction to a continental- island arc collision. The character of the incoming plate varies from the rough topography of the Roo Rise, to the smooth seafloor of the Abyssal Plain off Bali, Sumbawa. Forearc structures include well-developed forearc basins and an accretionary prism/outer forearc high of variable size and shape. To quantify the variability of structure of the lower plate and the effects on the upper plate a refraction seismic survey was carried during cruise SO190-2. A total of 245 ocean bottom seismometers were deployed along 1020 nm of wide-angle seismic profiles in four major north-south oriented corridors. To assess the velocity structure we used a tomographic method which jointly inverts for refracted and reflected phases. The sedimentary layers of the models, obtained by the analysis of high-resolution MCS data (see Lueschen et al), were incorporated into the starting model. The obtained models exhibit strong changes of the incoming oceanic crust for the different portions of the margin: The westernmost profile off eastern Java shows a crustal thickness of more than 15 km, most likely related to the presence of an oceanic plateau. Profiles off Lombok reveal an oceanic crust of 8-9 km average thickness in the Argo Abyssal Plain. Crustal and upper mantle velocities are slightly decreased within an area of about 50-60 km seaward of the trench, indicating fracturing and related serpentinization due to bending of the oceanic crust and associated normal faulting. The outer forearc high is characterized by velocities of 2.5-5.5 km/s. For the Lombok Basin, the profiles show a sedimentary infill of up to 3.5 km thick and typical sediment velocities of 1.75-3.0 km/s. A reflector at 16 km depth and velocity values of 7.4-7.8 km/s beneath it suggest the presence of a shallow

  13. Seismic modeling of multidimensional heterogeneity scales of Mallik gas hydrate reservoirs, Northwest Territories of Canada

    Science.gov (United States)

    Huang, Jun-Wei; Bellefleur, Gilles; Milkereit, Bernd

    2009-07-01

    In hydrate-bearing sediments, the velocity and attenuation of compressional and shear waves depend primarily on the spatial distribution of hydrates in the pore space of the subsurface lithologies. Recent characterizations of gas hydrate accumulations based on seismic velocity and attenuation generally assume homogeneous sedimentary layers and neglect effects from large- and small-scale heterogeneities of hydrate-bearing sediments. We present an algorithm, based on stochastic medium theory, to construct heterogeneous multivariable models that mimic heterogeneities of hydrate-bearing sediments at the level of detail provided by borehole logging data. Using this algorithm, we model some key petrophysical properties of gas hydrates within heterogeneous sediments near the Mallik well site, Northwest Territories, Canada. The modeled density, and P and S wave velocities used in combination with a modified Biot-Gassmann theory provide a first-order estimate of the in situ volume of gas hydrate near the Mallik 5L-38 borehole. Our results suggest a range of 528 to 768 × 106 m3/km2 of natural gas trapped within hydrates, nearly an order of magnitude lower than earlier estimates which did not include effects of small-scale heterogeneities. Further, the petrophysical models are combined with a 3-D finite difference modeling algorithm to study seismic attenuation due to scattering and leaky mode propagation. Simulations of a near-offset vertical seismic profile and cross-borehole numerical surveys demonstrate that attenuation of seismic energy may not be directly related to the intrinsic attenuation of hydrate-bearing sediments but, instead, may be largely attributed to scattering from small-scale heterogeneities and highly attenuate leaky mode propagation of seismic waves through larger-scale heterogeneities in sediments.

  14. Experimental processing of a model data set using Geobit seismic software

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Sang Yong [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    A seismic data processing software, Geobit, has been developed and is continuously updated to implement newer processing techniques and to support more hardware platforms. Geobit is intended to support all Unix platforms ranging from PC to CRAY. The current version supports two platform, i.e., PC/Linux and Sun Sparc based Sun OS 4.1.x. PC/Linux attracted geophysicists in some universities trying to install Geobit in their laboratories to be used as their research tool. However, one of the problem is the difficulty in getting the seismic data. The primary reason is its huge volume. The field data is too bulky to fit their relatively small storage media, such as PC disk. To solve the problem, KIGAM released a model seismic data set via ftp.kigam.re.kr. This study aims two purposes. The first one is testing Geobit software for its suitability in seismic data processing. The test includes reproducing the model through the seismic data processing. If it fails to reproduce the original model, the software is considered buggy and incomplete. However, if it can successfully reproduce the input model, I would be proud of what I have accomplished for the last few years in writing Geobit. The second purpose is to give a guide on Geobit usage by providing an example set of job files needed to process a given data. This example will help scientists lacking Geobit experience to concentrate on their study more easily. Once they know the Geobit processing technique, and later on Geobit programming, they can implement their own processing idea, contributing newer technologies to Geobit. The complete Geobit job files needed to process the model data is written, in the following job sequence: (1) data loading, (2) CDP sort, (3) decon analysis, (4) velocity analysis, (5) decon verification, (6) stack, (7) filter analysis, (8) filtered stack, (9) time migration, (10) depth migration. The control variables in the job files are discussed. (author). 10 figs., 1 tab.

  15. Realistic modeling of seismic input for megacities and large urban areas

    International Nuclear Information System (INIS)

    Panza, Giuliano F.; Alvarez, Leonardo; Aoudia, Abdelkrim

    2002-06-01

    The project addressed the problem of pre-disaster orientation: hazard prediction, risk assessment, and hazard mapping, in connection with seismic activity and man-induced vibrations. The definition of realistic seismic input has been obtained from the computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models. The innovative modeling technique, that constitutes the common tool to the entire project, takes into account source, propagation and local site effects. This is done using first principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. In fact, several techniques that have been proposed to empirically estimate the site effects using observations convolved with theoretically computed signals corresponding to simplified models, supply reliable information about the site response to non-interfering seismic phases. They are not adequate in most of the real cases, when the seismic sequel is formed by several interfering waves. The availability of realistic numerical simulations enables us to reliably estimate the amplification effects even in complex geological structures, exploiting the available geotechnical, lithological, geophysical parameters, topography of the medium, tectonic, historical, palaeoseismological data, and seismotectonic models. The realistic modeling of the ground motion is a very important base of knowledge for the preparation of groundshaking scenarios that represent a valid and economic tool for the seismic microzonation. This knowledge can be very fruitfully used by civil engineers in the design of new seismo-resistant constructions and in the reinforcement of the existing built environment, and, therefore

  16. Modeling the effects of structure on seismic anisotropy in the Chester gneiss dome, southeast Vermont

    Science.gov (United States)

    Saif, S.; Brownlee, S. J.

    2017-12-01

    Compositional and structural heterogeneity in the continental crust are factors that contribute to the complex expression of crustal seismic anisotropy. Understanding deformation and flow in the crust using seismic anisotropy has thus proven difficult. Seismic anisotropy is affected by rock microstructure and mineralogy, and a number of studies have begun to characterize the full elastic tensors of crustal rocks in an attempt to increase our understanding of these intrinsic factors. However, there is still a large gap in length-scale between laboratory characterization on the scale of centimeters and seismic wavelengths on the order of kilometers. To address this length-scale gap we are developing a 3D crustal model that will help us determine the effects of rotating laboratory-scale elastic tensors into field-scale structures. The Chester gneiss dome in southeast Vermont is our primary focus. The model combines over 2000 structural data points from field measurements and published USGS structural data with elastic tensors of Chester dome rocks derived from electron backscatter diffraction data. We created a uniformly spaced grid by averaging structural measurements together in equally spaced grid boxes. The surface measurements are then projected into the third dimension using existing subsurface interpretations. A measured elastic tensor for the specific rock type is rotated according to its unique structural input at each point in the model. The goal is to use this model to generate artificial seismograms using existing numerical wave propagation codes. Once completed, the model input can be varied to examine the effects of different subsurface structure interpretations, as well as heterogeneity in rock composition and elastic tensors. Our goal is to be able to make predictions for how specific structures will appear in seismic data, and how that appearance changes with variations in rock composition.

  17. A new approach to integrate seismic and production data in reservoir models

    Energy Technology Data Exchange (ETDEWEB)

    Ouenes, A.; Chawathe, A.; Weiss, W. [New Mexico Tech, Socorro, NM (United States)] [and others

    1997-08-01

    A great deal of effort is devoted to reducing the uncertainties in reservoir modeling. For example, seismic properties are used to improve the characterization of interwell properties by providing porosity maps constrained to seismic impedance. Another means to reduce uncertainties is to constrain the reservoir model to production data. This paper describes a new approach where the production and seismic data are simultaneously used to reduce the uncertainties. In this new approach, the primary geologic parameter that controls reservoir properties is identified. Next, the geophysical parameter that is sensitive to the dominant geologic parameter is determined. Then the geology and geophysics are linked using analytic correlations. Unfortunately, the initial guess resulted in a reservoir model that did not match the production history. Since the time required for trial and error matching of production history is exorbitant, an automatic history matching method based on a fast optimization method was used to find the correlating parameters. This new approach was illustrated with an actual field in the Williston Basin. Upscalling problems do not arise since the scale is imposed by the size of the seismic bin (66m, 219 ft) which is the size of the simulator gridblocks.

  18. Two-dimensional horizontal model seismic test and analysis for HTGR core

    International Nuclear Information System (INIS)

    Ikushima, Takeshi; Honma, Toshiaki.

    1988-05-01

    The resistance against earthquakes of high-temperature gas-cooled reactor (HTGR) core with block-type fuels is not fully ascertained yet. Seismic studies must be made if such a reactor plant is to be installed in areas with frequent earthquakes. The paper presented the test results of seismic behavior of a half scale two-dimensional horizontal slice core model and analysis. The following is a summary of the more important results. (1) When the core is subjected to the single axis excitation and simultaneous two-axis excitations to the core across-corners, it has elliptical motion. The core stays lumped motion at the low excitation frequencies. (2) When the load is placed on side fixed reflector blocks from outside to the core center, the core displacement and reflector impact reaction force decrease. (3) The maximum displacement occurs at simultaneous two-axis excitations. The maximum displacement occurs at the single axis excitation to the core across-flats. (4) The results of two-dimensional horizontal slice core model was compared with the results of two-dimensional vertical one. It is clarified that the seismic response of actual core can be predicted from the results of two-dimensional vertical slice core model. (5) The maximum reflector impact reaction force for seismic waves was below 60 percent of that for sinusoidal waves. (6) Vibration behavior and impact response are in good agreement between test and analysis. (author)

  19. Joint inversion of seismic refraction and resistivity data using layered models - applications to hydrogeology

    Science.gov (United States)

    Juhojuntti, N. G.; Kamm, J.

    2010-12-01

    We present a layered-model approach to joint inversion of shallow seismic refraction and resistivity (DC) data, which we believe is a seldom tested method of addressing the problem. This method has been developed as we believe that for shallow sedimentary environments (roughly fairly simple 2D geometries, mainly for checking the validity of the calculations. The inversion generally converges towards the correct solution, although there could be stability problems if the starting model is too erroneous. We have also applied the code to field data from seismic refraction and multi-electrode resistivity measurements at typical sand-gravel groundwater reservoirs. The tests are promising, as the calculated depths agree fairly well with information from drilling and the velocity and resistivity values appear reasonable. Current work includes better regularization of the inversion as well as defining individual weight factors for the different datasets, as the present algorithm tends to constrain the depths mainly by using the seismic data. More complex synthetic examples will also be tested, including models addressing the seismic hidden-layer problem.

  20. Formation of Ground Truth Databases and Related Studies and Regional Seismic Monitoring Research

    Science.gov (United States)

    2006-06-01

    experiments (1997-1999) in the former Semipalatinsk test site , Proceedings of the 22nd Annual DoDLDOE Seismic Research Symposium, Vol. I, U. S. Department of...DefenselEnergy, 55-66. Kim, Won-Young (1998), Waveform Data Information Product: Calibration Explosions at Semipalatinsk Test Site , Kazakstan...from the aftershocks of a 100 ton chemical explosion at the Degelen, Kazakh Test Site on 22 August 1998 (Omega-1). Epicentral locations, based on P

  1. The Physical Basis of the Explosion Source and Generation of Regional Seismic Phases

    Science.gov (United States)

    2007-08-31

    by the source S/P ratio for the Semipalatinsk and Lop Nor test sites . Fisk (2006) also found similar results at the Novaya Zemlya test site . These...area of the Semipalatinsk Test Site in Kazakhstan in the summer of 1997. Their primary purpose was to investigate the effects of depth of burial on...small magnitude seismic events during 1961-1989 on and near the Semipalatinsk Test Site , Kazakhstan, Pure and Appl. Geophy., 158, Issue 1-2,143-171

  2. Seismicity pattern: an indicator of source region of volcanism at convergent plate margins

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

    2004-01-01

    Roč. 141, č. 4 (2004), s. 303-326 ISSN 0031-9201 R&D Projects: GA AV ČR IAA3012002; GA AV ČR IAA3012303; GA AV ČR KSK3012103 Institutional research plan: CEZ:AV0Z3012916 Keywords : seismicity pattern * volcanism * aseismic gap Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.370, year: 2004

  3. Probabilistic Seismic Hazard Analysis for Yemen

    Directory of Open Access Journals (Sweden)

    Rakesh Mohindra

    2012-01-01

    Full Text Available A stochastic-event probabilistic seismic hazard model, which can be used further for estimates of seismic loss and seismic risk analysis, has been developed for the territory of Yemen. An updated composite earthquake catalogue has been compiled using the databases from two basic sources and several research publications. The spatial distribution of earthquakes from the catalogue was used to define and characterize the regional earthquake source zones for Yemen. To capture all possible scenarios in the seismic hazard model, a stochastic event set has been created consisting of 15,986 events generated from 1,583 fault segments in the delineated seismic source zones. Distribution of horizontal peak ground acceleration (PGA was calculated for all stochastic events considering epistemic uncertainty in ground-motion modeling using three suitable ground motion-prediction relationships, which were applied with equal weight. The probabilistic seismic hazard maps were created showing PGA and MSK seismic intensity at 10% and 50% probability of exceedance in 50 years, considering local soil site conditions. The resulting PGA for 10% probability of exceedance in 50 years (return period 475 years ranges from 0.2 g to 0.3 g in western Yemen and generally is less than 0.05 g across central and eastern Yemen. The largest contributors to Yemen’s seismic hazard are the events from the West Arabian Shield seismic zone.

  4. Characterization of tsunamigenic earthquake in Java region based on seismic wave calculation

    International Nuclear Information System (INIS)

    Pribadi, Sugeng; Afnimar,; Puspito, Nanang T.; Ibrahim, Gunawan

    2014-01-01

    This study is to characterize the source mechanism of tsunamigenic earthquake based on seismic wave calculation. The source parameter used are the ratio (Θ) between the radiated seismic energy (E) and seismic moment (M o ), moment magnitude (M W ), rupture duration (T o ) and focal mechanism. These determine the types of tsunamigenic earthquake and tsunami earthquake. We calculate the formula using the teleseismic wave signal processing with the initial phase of P wave with bandpass filter 0.001 Hz to 5 Hz. The amount of station is 84 broadband seismometer with far distance of 30° to 90°. The 2 June 1994 Banyuwangi earthquake with M W =7.8 and the 17 July 2006 Pangandaran earthquake with M W =7.7 include the criteria as a tsunami earthquake which distributed about ratio Θ=−6.1, long rupture duration To>100 s and high tsunami H>7 m. The 2 September 2009 Tasikmalaya earthquake with M W =7.2, Θ=−5.1 and To=27 s which characterized as a small tsunamigenic earthquake

  5. Characterization of tsunamigenic earthquake in Java region based on seismic wave calculation

    Energy Technology Data Exchange (ETDEWEB)

    Pribadi, Sugeng, E-mail: sugengpribadimsc@gmail.com [Badan Meteorologi Klimatologi Geofisika, Jl Angkasa I No. 2 Jakarta (Indonesia); Afnimar,; Puspito, Nanang T.; Ibrahim, Gunawan [Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24

    This study is to characterize the source mechanism of tsunamigenic earthquake based on seismic wave calculation. The source parameter used are the ratio (Θ) between the radiated seismic energy (E) and seismic moment (M{sub o}), moment magnitude (M{sub W}), rupture duration (T{sub o}) and focal mechanism. These determine the types of tsunamigenic earthquake and tsunami earthquake. We calculate the formula using the teleseismic wave signal processing with the initial phase of P wave with bandpass filter 0.001 Hz to 5 Hz. The amount of station is 84 broadband seismometer with far distance of 30° to 90°. The 2 June 1994 Banyuwangi earthquake with M{sub W}=7.8 and the 17 July 2006 Pangandaran earthquake with M{sub W}=7.7 include the criteria as a tsunami earthquake which distributed about ratio Θ=−6.1, long rupture duration To>100 s and high tsunami H>7 m. The 2 September 2009 Tasikmalaya earthquake with M{sub W}=7.2, Θ=−5.1 and To=27 s which characterized as a small tsunamigenic earthquake.

  6. Seismic Tomography of the Northwest Himalayas, Western Syntaxis and Pamir-Hindu Kush Region: Implications for Underlying Geodynamics

    Science.gov (United States)

    Raoof, J.; Mukhopadhyay, S.

    2017-12-01

    Travel time tomography of the study region using regional as well as local earthquake data illuminate a very heterogeneous structure of this geologically and tectonically complex region. The tomographic image is well resolved up to 150 km depth in the Western Himalayas and up to 300 km depth in the Pamir and Hindu Kush region. The top low velocity anomaly imaged up to 80 km depth correlates well with the thicker crust with deeper low density roots under the high mountains in the northwest Himalayas as well as in the Pamir and Hindu Kush region. Average crustal thickness increases from south to north in the Himalayas as well as along the tectonic trend of the Himalayas. This might be an effect of first collision between Indian and Eurasian plates in the NW and then subsequent anticlockwise rotation of Indian plate, leading to crumpling of the crust. This could also be due to variable thickness of more rigid portion of the incoming crust of Indian plate. The Indian lithospheric slab is imaged as a gently underthrusting high velocity anomaly under the northwest Himalayas and subducted Indian lithospheric slab which follows the trend of intermediate depth seismicity under the Pamir and Hindu Kush region. On the other hand beneath the Pamir-Tien Shan the dipping high velocity anomaly which follows the trend of intermediate depth seismicity, represents the remnant of the southward subducted Asian slab. In the southwest of Hindu Kush the Indian lithospheric slab rolls over and overturns at a depth of 250 km and dips southward. The Delhi-Haridwar Ridge (DHR) and Salt Ranges orthogonal to the strike of the Himalayas are well imaged as high velocity structures. The DHR is butting against the northwest Himalayas that led to ramming and locally buckling of the crust below the Higher Himalayas just NE of DHR. Seismicity pattern follows this trend of the crust. It shows for the first time the effect of ramming of the Himalayas by DHR and most importantly how the Indian plate

  7. Proterozoic structure, cambrian rifting, and younger faulting as revealed by a regional seismic reflection network in the Southern Illinois Basin

    Science.gov (United States)

    Potter, C.J.; Drahovzal, James A.; Sargent, M.L.; McBride, J.H.

    1997-01-01

    Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: 1. Prominent Proterozoic layering, possibly equivalent to Proterozoic (???1 Ga) Middle Run Formation clastic strata and underlying (1.3-1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. 2. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. 3. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. 4. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. 5. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. 6. Where crossed by the seismic reflection line in southeast Illinois, some

  8. Uppermost mantle seismic velocity and anisotropy in the Euro-Mediterranean region from Pn and Sn tomography

    Science.gov (United States)

    Díaz, J.; Gil, A.; Gallart, J.

    2013-01-01

    In the last 10-15 years, the number of high quality seismic stations monitoring the Euro-Mediterranean region has increased significantly, allowing a corresponding improvement in structural constraints. We present here new images of the seismic velocity and anisotropy variations in the uppermost mantle beneath this complex area, compiled from inversion of Pn and Sn phases sampling the whole region. The method of Hearn has been applied to the traveltime arrivals of the International Seismological Center catalogue for the time period 1990-2010. A total of 579 753 Pn arrivals coming from 12 377 events recorded at 1 408 stations with epicentral distances between 220 km and 1 400 km have been retained after applying standard quality criteria (maximum depth, minimum number of recordings, maximum residual values …). Our results show significant features well correlated with surface geology and evidence the heterogeneous character of the Euro-Mediterranean lithosphere. The station terms reflect the existence of marked variations in crustal thickness, consistent with available Moho depths inferred from active seismic experiments. The highest Pn velocities are observed along a continuous band from the Po Basin to the northern Ionian Sea. Other high velocity zones include the Ligurian Basin, the Valencia Trough, the southern Alboran Sea and central part of the Algerian margin. Most significant low-velocity values are associated to orogenic belts (Betics, Pyrenees, Alps, Apennines and Calabrian Arc, Dinarides-Hellenides), and low-velocity zones are also identified beneath Sardinia and the Balearic Islands. The introduction of an anisotropic term enhances significantly the lateral continuity of the anomalies, in particular in the most active tectonic areas. Pn anisotropy shows consistent orientations subparallel to major orogenic structures, such as Betics, Apennines, Calabrian Arc and Alps. The Sn tomographic image has lower resolution but confirms independently most of the

  9. One-dimensional modeling of thermal energy produced in a seismic fault

    Science.gov (United States)

    Konga, Guy Pascal; Koumetio, Fidèle; Yemele, David; Olivier Djiogang, Francis

    2017-12-01

    Generally, one observes an anomaly of temperature before a big earthquake. In this paper, we established the expression of thermal energy produced by friction forces between the walls of a seismic fault while considering the dynamic of a one-dimensional spring-block model. It is noted that, before the rupture of a seismic fault, displacements are caused by microseisms. The curves of variation of this thermal energy with time show that, for oscillatory and aperiodic displacement, the thermal energy is accumulated in the same way. The study reveals that thermal energy as well as temperature increases abruptly after a certain amount of time. We suggest that the corresponding time is the start of the anomaly of temperature observed which can be considered as precursory effect of a big seism. We suggest that the thermal energy can heat gases and dilate rocks until they crack. The warm gases can then pass through the cracks towards the surface. The cracks created by thermal energy can also contribute to the rupture of the seismic fault. We also suggest that the theoretical model of thermal energy, produced in seismic fault, associated with a large quantity of experimental data may help in the prediction of earthquakes.

  10. Realistic modelling of the seismic input: Site effects and parametric studies

    International Nuclear Information System (INIS)

    Romanelli, F.; Vaccari, F.; Panza, G.F.

    2002-11-01

    We illustrate the work done in the framework of a large international cooperation, showing the very recent numerical experiments carried out within the framework of the EC project 'Advanced methods for assessing the seismic vulnerability of existing motorway bridges' (VAB) to assess the importance of non-synchronous seismic excitation of long structures. The definition of the seismic input at the Warth bridge site, i.e. the determination of the seismic ground motion due to an earthquake with a given magnitude and epicentral distance from the site, has been done following a theoretical approach. In order to perform an accurate and realistic estimate of site effects and of differential motion it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters, in realistic geological structures. The computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different sources and structural models, allows us the construction of damage scenarios that are out of the reach of stochastic models, at a very low cost/benefit ratio. (author)

  11. Seismicity, focal mechanisms, and stress distribution in the Tres Virgenes volcanic and geothermal region, Baja California Sur, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Victor; Munguia, Luis [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada (Mexico)

    2006-01-15

    In October 1993 we carried out a seismic monitoring in the Tres Virgenes volcanic region in order to record the background seismicity associated with the volcanic structures, the geothermal field and the tectonic features of the area. Hypocenters for 257 microearthquakes were located in the volcanic edifices and along the northwest right-lateral, strike-slip La Virgen fault. Focal depths range from close to the Earth surface to about 8 km. Shallow depths occur mainly in the volcanic edifices. Deeper seismic events occurred outside the volcanic area. The duration magnitudes of the located microearthquakes range between 1 and 3. The Vp/Vs ratio and the low-Q values estimated suggest heterogeneous material properties in the volcanic structures mainly toward the El Azufre fault and the El Aguajito Caldera, where hydrothermal activity has been reported. The P- and T-axes of focal mechanisms for 90 microearthquakes suggest that the region is under N-S compression and E-W extension, in agreement with the regional tectonic stress field of the NW-SE right-lateral strike-slip transform fault system of the Gulf of California. [Spanish] En octubre de 1993 se llevo a cabo un monitoreo sismico en la region volcanica Las Tres Virgenes con el proposito de registrar la actividad sismica asociada a las estructuras volcanicas, al campo geotermico y a la tectonica local. Se localizaron 257 microsismos con hipocentros en los edificios volcanicos y a lo largo de la falla de rumbo, lateral derecha conocida como falla La Virgen. La profundidad focal de los sismos varia desde los muy cercanos a la superficie de la Tierra hasta los 8 km. Las profundidades someras ocurren principalmente en los edificios volcanicos. Los sismos mas profundos ocurren fuera del area volcanica. La magnitud de duracion de los microsismos localizados varia entre 1 y 3. La razon Vp/Vs y los valores bajos de Q que se estimaron en la zona sugieren un material con propiedades heterogeneas bajo las estructuras

  12. National Seismic Station

    International Nuclear Information System (INIS)

    Stokes, P.A.

    1982-06-01

    The National Seismic Station was developed to meet the needs of regional or worldwide seismic monitoring of underground nuclear explosions to verify compliance with a nuclear test ban treaty. The Station acquires broadband seismic data and transmits it via satellite to a data center. It is capable of unattended operation for periods of at least a year, and will detect any tampering that could result in the transmission of unauthentic seismic data

  13. Establishment of data base of regional seismic recordings from earthquakes, chemical explosions and nuclear explosions in the Former Soviet Union

    Energy Technology Data Exchange (ETDEWEB)

    Ermolenko, N.A.; Kopnichev, Yu.F.; Kunakov, V.G.; Kunakova, O.K.; Rakhmatullin, M.Kh.; Sokolova, I.N.; Vybornyy, Zh.I. [AN SSSR, Moscow (Russian Federation). Inst. Fiziki Zemli

    1995-06-01

    In this report results of work on establishment of a data base of regional seismic recordings from earthquakes, chemical explosions and nuclear explosions in the former Soviet Union are described. This work was carried out in the Complex Seismological Expedition (CSE) of the Joint Institute of Physics of the Earth of the Russian Academy of Sciences and Lawrence Livermore National Laboratory. The recording system, methods of investigations and primary data processing are described in detail. The largest number of digital records was received by the permanent seismic station Talgar, situated in the northern Tien Shan, 20 km to the east of Almaty city. More than half of the records are seismograms of underground nuclear explosions and chemical explosions. The nuclear explosions were recorded mainly from the Semipalatinsk test site. In addition, records of the explosions from the Chinese test site Lop Nor and industrial nuclear explosions from the West Siberia region were obtained. Four records of strong chemical explosions were picked out (two of them have been produced at the Semipalatinsk test site and two -- in Uzbekistan). We also obtained 16 records of crustal earthquakes, mainly from the Altai region, close to the Semipalatinsk test site, and also from the West China region, close to the Lop Nor test site. In addition, a small number of records of earthquakes and underground nuclear explosions, received by arrays of temporary stations, that have been working in the southern Kazakhstan region are included in this report. Parameters of the digital seismograms and file structure are described. Possible directions of future work on the digitizing of unique data archive are discussed.

  14. Seismic response analysis of reactor containment structures - axisymmetric model with modified ground motion

    International Nuclear Information System (INIS)

    Saha, S.; Dasgupta, A.; Basu, P.C.

    1993-01-01

    Seismic analysis of a Reactor Building is performed idealising the system as a beam model (BM) and also an Axi-symmetric model (ASM) and the results compared. In both the cases effect of Soil-Structure Interaction have been taken Into account. Since the lower boundary of the ASM was at a depth much lower than that of the BM, deconvolution of the specified Free-Field Motion (FFM) was necessary. The deconvolution has been performed using frequency domain approach. (author)

  15. Seismic behavior of an Italian Renaissance Sanctuary: Damage assessment by numerical modelling

    Science.gov (United States)

    Clementi, Francesco; Nespeca, Andrea; Lenci, Stefano

    2016-12-01

    The paper deals with modelling and analysis of architectural heritage through the discussion of an illustrative case study: the Medieval Sanctuary of Sant'Agostino (Offida, Italy). Using the finite element technique, a 3D numerical model of the sanctuary is built, and then used to identify the main sources of the damages. The work shows that advanced numerical analyses could offer significant information for the understanding of the causes of existing damage and, more generally, on the seismic vulnerability.

  16. Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

    Science.gov (United States)

    Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

    2007-05-01

    Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

  17. Seismic modeling with radial basis function-generated finite differences (RBF-FD) – a simplified treatment of interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Bradley, E-mail: brma7253@colorado.edu; Fornberg, Bengt, E-mail: Fornberg@colorado.edu

    2017-04-15

    In a previous study of seismic modeling with radial basis function-generated finite differences (RBF-FD), we outlined a numerical method for solving 2-D wave equations in domains with material interfaces between different regions. The method was applicable on a mesh-free set of data nodes. It included all information about interfaces within the weights of the stencils (allowing the use of traditional time integrators), and was shown to solve problems of the 2-D elastic wave equation to 3rd-order accuracy. In the present paper, we discuss a refinement of that method that makes it simpler to implement. It can also improve accuracy for the case of smoothly-variable model parameter values near interfaces. We give several test cases that demonstrate the method solving 2-D elastic wave equation problems to 4th-order accuracy, even in the presence of smoothly-curved interfaces with jump discontinuities in the model parameters.

  18. Using finite-difference waveform modeling to better understand rupture kinematics and path effects in ground motion modeling: an induced seismicity case study at the Groningen Gas field

    Science.gov (United States)

    Zurek, B.; Burnett, W. A.; deMartin, B.

    2017-12-01

    Ground motion models (GMMs) have historically been used as input in the development of probabilistic seismic hazard analysis (PSHA) and as an engineering tool to assess risk in building design. Generally these equations are developed from empirical analysis of observations that come from fairly complete catalogs of seismic events. One of the challenges when doing a PSHA analysis in a region where earthquakes are anthropogenically induced is that the catalog of observations is not complete enough to come up with a set of equations to cover all expected outcomes. For example, PSHA analysis at the Groningen gas field, an area of known induced seismicity, requires estimates of ground motions from tremors up to a maximum magnitude of 6.5 ML. Of the roughly 1300 recordable earthquakes the maximum observed magnitude to date has been 3.6ML. This paper is part of a broader study where we use a deterministic finite-difference wave-form modeling tool to compliment the traditional development of GMMs. Of particular interest is the sensitivity of the GMM's to uncertainty in the rupture process and how this scales to larger magnitude events that have not been observed. A kinematic fault rupture model is introduced to our waveform simulations to test the sensitivity of the GMMs to variability in the fault rupture process that is physically consistent with observations. These tests will aid in constraining the degree of variability in modeled ground motions due to a realistic range of fault parameters and properties. From this study it is our conclusion that in order to properly capture the uncertainty of the GMMs with magnitude up-scaling one needs to address the impact of uncertainty in the near field (risk. Further, by investigating and constraining the range of fault rupture scenarios and earthquake magnitudes on ground motion models, hazard and risk analysis in regions with incomplete earthquake catalogs, such as the Groningen gas field, can be better understood.

  19. When probabilistic seismic hazard climbs volcanoes: the Mt. Etna case, Italy – Part 1: Model components for sources parameterization

    Directory of Open Access Journals (Sweden)

    R. Azzaro

    2017-11-01

    Full Text Available The volcanic region of Mt. Etna (Sicily, Italy represents a perfect lab for testing innovative approaches to seismic hazard assessment. This is largely due to the long record of historical and recent observations of seismic and tectonic phenomena, the high quality of various geophysical monitoring and particularly the rapid geodynamics clearly demonstrate some seismotectonic processes. We present here the model components and the procedures adopted for defining seismic sources to be used in a new generation of probabilistic seismic hazard assessment (PSHA, the first results and maps of which are presented in a companion paper, Peruzza et al. (2017. The sources include, with increasing complexity, seismic zones, individual faults and gridded point sources that are obtained by integrating geological field data with long and short earthquake datasets (the historical macroseismic catalogue, which covers about 3 centuries, and a high-quality instrumental location database for the last decades. The analysis of the frequency–magnitude distribution identifies two main fault systems within the volcanic complex featuring different seismic rates that are controlled essentially by volcano-tectonic processes. We discuss the variability of the mean occurrence times of major earthquakes along the main Etnean faults by using an historical approach and a purely geologic method. We derive a magnitude–size scaling relationship specifically for this volcanic area, which has been implemented into a recently developed software tool – FiSH (Pace et al., 2016 – that we use to calculate the characteristic magnitudes and the related mean recurrence times expected for each fault. Results suggest that for the Mt. Etna area, the traditional assumptions of uniform and Poissonian seismicity can be relaxed; a time-dependent fault-based modeling, joined with a 3-D imaging of volcano-tectonic sources depicted by the recent instrumental seismicity, can therefore be

  20. Integrated Reflection Seismic Monitoring and Reservoir Modeling for Geologic CO2 Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    John Rogers

    2011-12-31

    The US DOE/NETL CCS MVA program funded a project with Fusion Petroleum Technologies Inc. (now SIGMA) to model the proof of concept of using sparse seismic data in the monitoring of CO{sub 2} injected into saline aquifers. The goal of the project was to develop and demonstrate an active source reflection seismic imaging strategy based on deployment of spatially sparse surface seismic arrays. The primary objective was to test the feasibility of sparse seismic array systems to monitor the CO{sub 2} plume migration injected into deep saline aquifers. The USDOE/RMOTC Teapot Dome (Wyoming) 3D seismic and reservoir data targeting the Crow Mountain formation was used as a realistic proxy to evaluate the feasibility of the proposed methodology. Though the RMOTC field has been well studied, the Crow Mountain as a saline aquifer has not been studied previously as a CO{sub 2} sequestration (storage) candidate reservoir. A full reprocessing of the seismic data from field tapes that included prestack time migration (PSTM) followed by prestack depth migration (PSDM) was performed. A baseline reservoir model was generated from the new imaging results that characterized the faults and horizon surfaces of the Crow Mountain reservoir. The 3D interpretation was integrated with the petrophysical data from available wells and incorporated into a geocellular model. The reservoir structure used in the geocellular model was developed using advanced inversion technologies including Fusion's ThinMAN{trademark} broadband spectral inversion. Seal failure risk was assessed using Fusion's proprietary GEOPRESS{trademark} pore pressure and fracture pressure prediction technology. CO{sub 2} injection was simulated into the Crow Mountain with a commercial reservoir simulator. Approximately 1.2MM tons of CO{sub 2} was simulated to be injected into the Crow Mountain reservoir over 30 years and subsequently let 'soak' in the reservoir for 970 years. The relatively small plume

  1. Numerical calculation models of the elastoplastic response of a structure under seismic action

    International Nuclear Information System (INIS)

    Edjtemai, Nima.

    1982-06-01

    Two digital calculation models developed in this work have made it possible to analyze the exact dynamic behaviour of ductile structures with one or several degrees of liberty, during earthquakes. With the first model, response spectra were built in the linear and non-linear fields for different absorption and ductility values and two types of seismic accelerograms. The comparative study of these spectra made it possible to check the validity of certain hypotheses suggested for the construction of elastoplastic spectra from corresponding linear spectra. A simplified method of non-linear seismic calculation based on the modal analysis and the spectra of elastoplastic response was then applied to structures with a varying number of degrees of liberty. The results obtained in this manner were compared with those provided by an exact calculation provided by the second digital model developed by us [fr

  2. Estimation of recurrence interval of large earthquakes on the central Longmen Shan fault zone based on seismic moment accumulation/release model.

    Science.gov (United States)

    Ren, Junjie; Zhang, Shimin

    2013-01-01

    Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 10¹⁷ N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  3. Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan Fault Zone Based on Seismic Moment Accumulation/Release Model

    Directory of Open Access Journals (Sweden)

    Junjie Ren

    2013-01-01

    Full Text Available Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9 occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF and the Guanxian-Jiangyou fault (GJF. However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS and Interferometric Synthetic Aperture Radar (InSAR data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3 × 1017 N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  4. Seismic modeling of fluvial-estuarine deposits in the Athabasca oil sands using ray-tracing techniques, Steepbank River area, northeastern Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Langenberg, C. W.; Hein, F. J. [Alberta Energy and Utilities Board, Edmonton, AB (Canada); Lawton, D.; Cunningham, J. [Calgary Univ., Dept. of Geology and Geophysics, Calgary, AB (Canada)

    2002-03-01

    Seismic reflection characteristics of contrasting channel geometries in a five-section portion of the Steepbank River are modeled using ray-tracing techniques. Outcrop lithofacies associations are used to create a seismic model that can be used as a subsurface analog of other similar oil-sands successions. At least four channel complexes based on stratal bounding surfaces, arrangement of lithofacies, and consistent paleoflow patterns have been identified. The lower part of each channel complex contains trough crossbedded sandstone, exhibiting high porosity and permeability. These sandstones were deposited in channel axes and are the highest grade bitumen deposits in the area. The upper parts of the channels contain significantly lower bitumen saturation values due to common interbedded mudstone. Nearby wells contain cored and logged intervals that are similar to exposed outcrops in the riverbank. Overall modeling results indicate that channel complexes can be imaged seismically, given data of sufficient quality and frequency. Bitumen grade may be predicted in these seismic lines, which has important consequences for bitumen exploration and extraction in the Steepbank River region. 64 refs., 26 figs.

  5. Modeling Seismic Cycles of Great Megathrust Earthquakes Across the Scales With Focus at Postseismic Phase

    Science.gov (United States)

    Sobolev, Stephan V.; Muldashev, Iskander A.

    2017-12-01

    Subduction is substantially multiscale process where the stresses are built by long-term tectonic motions, modified by sudden jerky deformations during earthquakes, and then restored by following multiple relaxation processes. Here we develop a cross-scale thermomechanical model aimed to simulate the subduction process from 1 min to million years' time scale. The model employs elasticity, nonlinear transient viscous rheology, and rate-and-state friction. It generates spontaneous earthquake sequences and by using an adaptive time step algorithm, recreates the deformation process as observed naturally during the seismic cycle and multiple seismic cycles. The model predicts that viscosity in the mantle wedge drops by more than three orders of magnitude during the great earthquake with a magnitude above 9. As a result, the surface velocities just an hour or day after the earthquake are controlled by viscoelastic relaxation in the several hundred km of mantle landward of the trench and not by the afterslip localized at the fault as is currently believed. Our model replicates centuries-long seismic cycles exhibited by the greatest earthquakes and is consistent with the postseismic surface displacements recorded after the Great Tohoku Earthquake. We demonstrate that there is no contradiction between extremely low mechanical coupling at the subduction megathrust in South Chile inferred from long-term geodynamic models and appearance of the largest earthquakes, like the Great Chile 1960 Earthquake.

  6. AxiSEM3D: broadband seismic wavefields in 3-D aspherical Earth models

    Science.gov (United States)

    Leng, K.; Nissen-Meyer, T.; Zad, K. H.; van Driel, M.; Al-Attar, D.

    2017-12-01

    Seismology is the primary tool for data-informed inference of Earth structure and dynamics. Simulating seismic wave propagation at a global scale is fundamental to seismology, but remains as one of most challenging problems in scientific computing, because of both the multiscale nature of Earth's interior and the observable frequency band of seismic data. We present a novel numerical method to simulate global seismic wave propagation in realistic 3-D Earth models. Our method, named AxiSEM3D, is a hybrid of spectral element method and pseudospectral method. It reduces the azimuthal dimension of wavefields by means of a global Fourier series parameterization, of which the number of terms can be locally adapted to the inherent azimuthal smoothness of the wavefields. AxiSEM3D allows not only for material heterogeneities, such as velocity, density, anisotropy and attenuation, but also for finite undulations on radial discontinuities, both solid-solid and solid-fluid, and thereby a variety of aspherical Earth features such as ellipticity, topography, variable crustal thickness, and core-mantle boundary topography. Such interface undulations are equivalently interpreted as material perturbations of the contiguous media, based on the "particle relabelling transformation". Efficiency comparisons show that AxiSEM3D can be 1 to 3 orders of magnitude faster than conventional 3-D methods, with the speedup increasing with simulation frequency and decreasing with model complexity, but for all realistic structures the speedup remains at least one order of magnitude. The observable frequency range of global seismic data (up to 1 Hz) has been covered for wavefield modelling upon a 3-D Earth model with reasonable computing resources. We show an application of surface wave modelling within a state-of-the-art global crustal model (Crust1.0), with the synthetics compared to real data. The high-performance C++ code is released at github.com/AxiSEM3D/AxiSEM3D.

  7. Investigations of the low frequency seismic waves recorded at near-regional distances from the Non-Proliferation Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Patton, H.J. [Lawrence Livermore National Lab., CA (United States)

    1994-12-31

    Seismic waves recorded at near-regional distances are used to characterize the source of the Non-Proliferation Experiment (NPE) and three selected nuclear explosions detonated in N-tunnel on Rainier Mesa. For periods longer than 5 sec, the signal-to-noise ratio is poor on most recordings of the NPE. A seismogram-stacking method is used in order to reduce background noise in coherent arrivals of Rayleigh waves. This method requires equalization of path dispersion and attenuation, which is accomplished in this study with empirical Green`s functions. The stacked, equalized Rayleigh-wave spectra are inverted, along with the spectral amplitudes of Lg waves with periods of 2-5 sec, for estimates of the seismic moment tensor. The NPE isotropic moment is 1.6 x 10{sup 14} Nt-m. The inferred static level of the reduced displacement potential is 825 m{sup 3}, which is about two times smaller than the estimate from free-field data recorded within 1 km of the NPE. Moment tensors of the NPE and nuclear explosions are asymmetric, describing prolate ellipsoids of rotation with the long axis in the vertical direction. The asymmetries are among the largest for explosions on Pahute and Rainier Mesa. The non-isotropic component is a compensated linear vector dipole (CLVD), which may represent driven block motions occurring within a conical volume of material extending from the shot point (apex) to the free surface. The CLVD source can help explain some observations of scalloping in the spectra of Lg waves and Lg spectral ratios. Seismic radiation from the NPE is virtually indistinguishable from that of nearby nuclear explosions for frequencies below 1 Hz.

  8. Processing of noisy magnetotelluric time series from Koyna-Warna seismic region, India: a systematic approach

    Directory of Open Access Journals (Sweden)

    Ujjal K. Borah

    2015-06-01

    Full Text Available Rolling array pattern broad band magnetotelluric (MT data was acquired in the Koyna-Warna (Maharashtra, India seismic zone during 2012-14 field campaigns. The main objective of this study is to identify the thickness of the Deccan trap in and around the Koyna-Warna seismic zone and to delineate the electrical nature of the sub-basalt. The MT data at many places got contaminated with high tension power line noise due to Koyna hydroelectric power project. So, in the present study an attempt has been made to tackle this problem due to 50 Hz noise and their harmonics and other cultural noise using commercially available processing software MAPROS. Remote site was running during the entire field period to stand against the cultural noise problem. This study is based on Fast Fourier Transform (FFT and mainly focuses on the behaviour of different processing parameters, their interrelations and the influences of different processing methods concerning improvement of the S/N ratio of noisy data. Our study suggests that no single processing approach can give desirable transfer functions, however combination of different processing approaches may be adopted while processing culturally affected noisy data.

  9. Evaluation of high frequency ghost cavitation emissions for two different seismic air-gun arrays using numerical modelling

    Science.gov (United States)

    Khodabandeloo, Babak; Landrø, Martin

    2017-04-01

    Sound is deployed by marine mammals for variety of vital purposes such as finding food, communication, echolocation, etc. On the other hand human activities generate underwater noise. One major type of acoustic source is marine seismic acquisition which is carried out to image layers beneath the seabed exploiting reflected acoustic and elastic waves. Air-gun arrays are the most common and efficient marine seismic sources. Field measurements using broad band hydrophones have revealed that acoustic energies emitted by air-gun arrays contains frequencies from a few Hz up to tens of kHz. Frequencies below 200 Hz benefit seismic imaging and the rest is normally considered as wasted energy. On the other hand, the high frequency range (above 200 Hz) overlaps with hearing curves of many marine mammals and especially toothed whales and may have an impact on their behavior. A phenomenon called ghost cavitation is recently recognized to be responsible for a major part of these high frequencies (> 5 kHz). Acoustic pressure waves of individual air guns reflected from sea surface can cause the hydrostatic pressure to drop towards zero close to the source array. In these regions there is a high probability for water vapor cavity growth and subsequent collapse. We have simulated ghost cavitation cloud using numerical modelling and the results are validated by comparing with field measurements. The model is used to compare the amount of high frequency noise due to ghost cavitation for two different air gun arrays. Both of the arrays have three subarrays but the array distance for the one with 2730 in3 air volume is 6 meters and for the slightly bigger array (3250 in3 in air volume) the subarrays are separated by 8 meters. Simulation results indicate that the second array, despite larger subarray distance, generates stronger ghost cavitation signal.

  10. A comparative study of two statistical approaches for the analysis of real seismicity sequences and synthetic seismicity generated by a stick-slip experimental model

    Science.gov (United States)

    Flores-Marquez, Leticia Elsa; Ramirez Rojaz, Alejandro; Telesca, Luciano

    2015-04-01

    The study of two statistical approaches is analyzed for two different types of data sets, one is the seismicity generated by the subduction processes occurred at south Pacific coast of Mexico between 2005 and 2012, and the other corresponds to the synthetic seismic data generated by a stick-slip experimental model. The statistical methods used for the present study are the visibility graph in order to investigate the time dynamics of the series and the scaled probability density function in the natural time domain to investigate the critical order of the system. This comparison has the purpose to show the similarities between the dynamical behaviors of both types of data sets, from the point of view of critical systems. The observed behaviors allow us to conclude that the experimental set up globally reproduces the behavior observed in the statistical approaches used to analyses the seismicity of the subduction zone. The present study was supported by the Bilateral Project Italy-Mexico Experimental Stick-slip models of tectonic faults: innovative statistical approaches applied to synthetic seismic sequences, jointly funded by MAECI (Italy) and AMEXCID (Mexico) in the framework of the Bilateral Agreement for Scientific and Technological Cooperation PE 2014-2016.

  11. Sensitivity of seismic design parameters to input variables

    International Nuclear Information System (INIS)

    Wium, D.J.W.

    1987-01-01

    The probabilistic method introduced by Cornell (1968) has been used to a large extent for this purpose. Due to its probabilistic approach, this technique provides a sound basis for studying the influence of the dominant parameters in such a model. Although the Southern African region is not well known for its seismicity, a number of events in the recent past has focussed the attention on some seismically active areas where special attention may be needed in defining the correct design parameters. The relatively sparse historical seismic data has been used to develop a mathematical model which represents this region. This paper briefly discusses this model, and uses it as a basis for evaluating the influence of the uncertainty in each of the principal parameters, being the seismicity of the region, the attenuation of seismic waves after an event, and models that can be used to arrive at engineering design values. (orig./HP)

  12. Validation of PWR core seismic models with shaking table tests on interacting scale 1 fuel assemblies

    International Nuclear Information System (INIS)

    Viallet, E.; Bolsee, G.; Ladouceur, B.; Goubin, T.; Rigaudeau, J.

    2003-01-01

    The fuel assembly mechanical strength must be justified with respect to the lateral loads under accident conditions, in particular seismic loads. This justification is performed by means of time-history analyses with dynamic models of an assembly row in the core, allowing for assembly deformations, impacts at grid locations and reactor coolant effects. Due to necessary simplifications, the models include 'equivalent' parameters adjusted with respect to dynamic characterisation tests of the fuel assemblies. Complementing such tests on isolated assemblies by an overall model validation with shaking table tests on interacting assemblies is obviously desirable. Seismic tests have been performed by French CEA (Commissariat a l'Energie Atomique) on a row of six full scale fuel assemblies, including two types of 17 x 17 12ft design. The row models are built according to the usual procedure, with preliminary characterisation tests performed on a single assembly. The test-calculation comparisons are made for two test configurations : in air and in water. The relatively large number of accelerograms (15, used for each configuration) is also favourable to significant comparisons. The results are presented for the impact forces at row ends, displacements at mid assembly, and also 'statistical' parameters. Despite a non-negligible scattering in the results obtained with different accelerograms, the calculations prove realistic, and the modelling process is validated with a good confidence level. This satisfactory validation allows to evaluate precisely the margins in the seismic design methodology of the fuel assemblies, and thus to confirm the safety of the plants in case of seismic event. (author)

  13. Seismic response of base-isolated buildings using a viscoelastic model

    International Nuclear Information System (INIS)

    Uras, R.A.

    1993-01-01

    Due to recent developments in elastomer technology,seismic isolation using elastomer bearings is rapidly gaining acceptance as a design tool to enhance structural seismic margins and to protect people and equipment from earthquake damage. With proper design of isolators, the fundamental frequency of the structure can be reduced to a value that is lower than the dominant frequencies of earthquake ground motions. The other feature of an isolation system is that it can provide a mechanism for energy dissipation. In the USA, the use of seismic base-isolation has become an alternate strategy for advanced Liquid Metal-cooled Reactors (LMRs). ANL has been deeply involved in the development and implementation of seismic isolation for use in both nuclear facilities and civil structures for the past decade. Shimizu Corporation of Japan has a test facility at Tohoku University in Sendai, Japan. The test facility has two buildings: one is base isolated and the other is conventionally founded. The buildings are full-size, three-story reinforced concrete structures. The dimensions and construction of the superstructures are identical. They were built side by side in a seismically active area. In 1988, the ANL/Shimizu Joint Program was established to study the differences in behavior of base-isolated and ordinarily founded structures when subjected to earthquake loading. A more comprehensive description of this joint program is presented in a companion paper (Wang et al. 1993). With the increased use of elastomeric polymers in industrial applications such as isolation bearings, the importance of constitutive modeling of viscoelastic materials is more and more pronounced. A realistic representation of material behavior is essential for computer simulations to replicate the response observed in experiments

  14. New insights into the 2012 Emilia (Italy) seismic sequence through advanced numerical modeling of ground deformation InSAR measurements

    Science.gov (United States)

    Tizzani, P.; Castaldo, R.; Solaro, G.; Pepe, S.; Bonano, M.; Casu, F.; Manunta, M.; Manzo, M.; Pepe, A.; Samsonov, S.; Lanari, R.; Sansosti, E.

    2013-05-01

    We provide new insights into the two main seismic events that occurred in 2012 in the Emilia region, Italy. We extend the results from previous studies based on analytical inversion modeling of GPS and RADARSAT-1 InSAR measurements by exploiting RADARSAT-2 data. Moreover, we benefit from the available large amount of geological and geophysical information through finite element method (FEM) modeling implemented in a structural-mechanical context to investigate the impact of known buried structures on the modulation of the ground deformation field. We find that the displacement pattern associated with the 20 May event is consistent with the activation of a single fault segment of the inner Ferrara thrust, in good agreement with the analytical solution. In contrast, the interpretation of the 29 May episode requires the activation of three different fault segments and a block roto-translation of the Mirandola anticline. The proposed FEM-based methodology is applicable to other seismic areas where the complexity of buried structures is known and plays a fundamental role in the modulation of the associated surface deformation pattern.

  15. Soil structure interaction model and variability of parameters in seismic analysis of nuclear island connected building

    International Nuclear Information System (INIS)

    Subramanian, K.V.; Palekar, S.M.; Bavare, M.S.; Mapari, H.A.; Patel, S.C.; Pillai, C.S.

    2005-01-01

    This paper provides salient features of the Soil Structure Interaction analysis of Nuclear Island Connected Building (NICB). The dynamic analysis of NICB is performed on a full 3D model accounting for the probable variation in the stiffness of the founding medium. A range analyses was performed to establish the effect of variability of subgrade parameters on the results of seismic analyses of NICB. This paper presents details of various analyses with respect to the subgrade model, uncertainties in subgrade properties, results of seismic analyses and a study of effect of the variability of parameters on the results of these analyses. The results of this study indicate that the variability of soil parameters beyond a certain value of shear wave velocity does not influence the response and in fact the response marginally diminishes. (authors)

  16. Modeling of the Sedimentary Interbedded Basalt Stratigraphy for the Idaho National Laboratory Probabilistic Seismic Hazard Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Suzette Payne

    2006-04-01

    This report summarizes how the effects of the sedimentary interbedded basalt stratigraphy were modeled in the probabilistic seismic hazard analysis (PSHA) of the Idaho National Laboratory (INL). Drill holes indicate the bedrock beneath INL facilities is composed of about 1.1 km of alternating layers of basalt rock and loosely consolidated sediments. Alternating layers of hard rock and “soft” loose sediments tend to attenuate seismic energy greater than uniform rock due to scattering and damping. The INL PSHA incorporated the effects of the sedimentary interbedded basalt stratigraphy by developing site-specific shear (S) wave velocity profiles. The profiles were used in the PSHA to model the near-surface site response by developing site-specific stochastic attenuation relationships.

  17. Modeling of the Sedimentary Interbedded Basalt Stratigraphy for the Idaho National Laboratory Probabilistic Seismic Hazard Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Suzette Payne

    2007-08-01

    This report summarizes how the effects of the sedimentary interbedded basalt stratigraphy were modeled in the probabilistic seismic hazard analysis (PSHA) of the Idaho National Laboratory (INL). Drill holes indicate the bedrock beneath INL facilities is composed of about 1.1 km of alternating layers of basalt rock and loosely consolidated sediments. Alternating layers of hard rock and “soft” loose sediments tend to attenuate seismic energy greater than uniform rock due to scattering and damping. The INL PSHA incorporated the effects of the sedimentary interbedded basalt stratigraphy by developing site-specific shear (S) wave velocity profiles. The profiles were used in the PSHA to model the near-surface site response by developing site-specific stochastic attenuation relationships.

  18. Applicability of fiber model in seismic response analysis for center-clamp type bushings on transformers

    International Nuclear Information System (INIS)

    Miyagawa, Yoshinori; Sato, Hiroaki

    2015-01-01

    A bushing is a device for insulation and support of a conductor. Especially it is called center-clamp type when it is connected with a metal holder through clamping force. As a consequence of damage of center-clamp type bushings in Tohoku Earthquake in 2011, refinement of the response analysis method and review of the seismic design procedure became necessary. In the present report, the fiber model, which can evaluate non-linear behavior in the section subjected to axial force and bending moment, was implemented to the CRIEPI's finite element analysis program 'Mastrd' considering following characteristics of center-clamp type bushings. a) The gasket section between a porcelain tube and a metal holder has a torus shape. b) Springs around the top of the bushing give clamping force, but they lock in excessive base rotation. c) The gasket does not resist against tension. d) Local resistance against compression due to bending increases in use of very thin gaskets. The developed program was verified through comparison with the shaking table test result for real bushings whose voltage classes were 154 kV and 275 kV. Deformation indices as rotation angle and base opening due to bending were influenced by damping conditions. Though there was not the condition which brought about remarkable underestimation, reduction of damping for a fiber model element was preferable for safety. On the other hand, bending moment was consistent with experimental results because it tended not to fluctuate in the non-linear region. (author)

  19. Application of thermodynamics-based rate-dependent constitutive models of concrete in the seismic analysis of concrete dams

    Directory of Open Access Journals (Sweden)

    Leng Fei

    2008-09-01

    Full Text Available This paper discusses the seismic analysis of concrete dams with consideration of material nonlinearity. Based on a consistent rate-dependent model and two thermodynamics-based models, two thermodynamics-based rate-dependent constitutive models were developed with consideration of the influence of the strain rate. They can describe the dynamic behavior of concrete and be applied to nonlinear seismic analysis of concrete dams taking into account the rate sensitivity of concrete. With the two models, a nonlinear analysis of the seismic response of the Koyna Gravity Dam and the Dagangshan Arch Dam was conducted. The results were compared with those of a linear elastic model and two rate-independent thermodynamics-based constitutive models, and the influences of constitutive models and strain rate on the seismic response of concrete dams were discussed. It can be concluded from the analysis that, during seismic response, the tensile stress is the control stress in the design and seismic safety evaluation of concrete dams. In different models, the plastic strain and plastic strain rate of concrete dams show a similar distribution. When the influence of the strain rate is considered, the maximum plastic strain and plastic strain rate decrease.

  20. Shortcomings of the Winkler Model in the Assessment of Sectioned Tunnels under Seismic Loading

    DEFF Research Database (Denmark)

    Andersen, Lars; Lyngs, J. H.

    2009-01-01

    A Winkler-type model is often applied in the design of tunnels subject to seismic loading. Since the subgrade stiffness is modelled by disjoint springs, distributed continuously along the tunnel, the model does not account for retroaction via the soil. This may not be a problem in the design......-element solution, using a planned tunnel at Thessaloniki, Greece, as a case study. The aim of the analysis is to quantify the inaccuracy of the Winkler model in the prediction of damage at a gasket between two tunnel elements....

  1. Shortcomings of the Winkler Model in the Assessment of Sectioned Tunnels under Seismic Loading

    DEFF Research Database (Denmark)

    Andersen, Lars; Lyngs, Jakob Hausgaard

    A Winkler-type model is often applied in the design of tunnels subject to seismic loading. Since the subgrade stiffness is modelled by disjoint springs, distributed continuously along the tunnel, the model does not account for retroaction via the soil. This may not be a problem in the design......-element solution, using a planned tunnel at Thessaloniki, Greece, as a case study. The aim of the analysis is to quantify the inaccuracy of the Winkler model in the prediction of damage at a gasket between two tunnel elements....

  2. Improving seismic crustal models in the Corinth Gulf, Greece and estimating source depth using PL-waves

    Science.gov (United States)

    Vackář, Jiří; Zahradník, Jiří

    2013-04-01

    A recent shallow earthquake in the Corinth Gulf, Greece (Mw 5.3, January 18, 2010; Sokos et al., Tectonophysics 2012) generated unusual long-period waves (periods > 5 seconds), well recorded at several near-regional stations between the P - and S-wave arrival. The 5-second period, being significantly longer than the source duration, indicates a structural effect. The wave is similar to PL-wave or Pnl-wave, but with shorter periods and observed in much closer distances (ranging from 30 to 200 km). For theoretical description of the observed wave, structural model is required. No existing regional crustal model generates that wave, so we need to find another model, better in terms of the PL-wave existence and strength. We find such models by full waveform inversion using the subset of stations with strong PL-wave. The Discrete Wavenumber method (Bouchon, 1981; Coutant 1989) is used for forward problem and the Neighborhood Algorithm (Sambridge, 1999) for stochastic search (more details in poster by V. Plicka and J. Zahradník). We obtain a suite of models well fitting synthetic seismograms and use some of these models to evaluate dependence of the studied waves on receiver distance and azimuth as well as dependence on source depth. We compare real and synthetic dispersion curves (derived from synthetic seismograms) as an independent validation of found model and discuss limitations of using dispersion curves for these cases. We also relocated the event in the new model. Then we calculate the wavefield by two other methods: modal summation and ray theory to better understand the nature of the PL-wave. Finally, we discuss agreement of found models with published crustal models in the region. The full waveform inversion for structural parameters seems to be powerful tool for improving seismic source modeling in cases we do not have accurate structure model of studied area. We also show that the PL-wave strength has a potential to precise the earthquake depth

  3. Effects of Source RDP Models and Near-source Propagation: Implication for Seismic Yield Estimation

    Science.gov (United States)

    Saikia, C. K.; Helmberger, D. V.; Stead, R. J.; Woods, B. B.

    - It has proven difficult to uniquely untangle the source and propagation effects on the observed seismic data from underground nuclear explosions, even when large quantities of near-source, broadband data are available for analysis. This leads to uncertainties in our ability to quantify the nuclear seismic source function and, consequently the accuracy of seismic yield estimates for underground explosions. Extensive deterministic modeling analyses of the seismic data recorded from underground explosions at a variety of test sites have been conducted over the years and the results of these studies suggest that variations in the seismic source characteristics between test sites may be contributing to the observed differences in the magnitude/yield relations applicable at those sites. This contributes to our uncertainty in the determination of seismic yield estimates for explosions at previously uncalibrated test sites. In this paper we review issues involving the relationship of Nevada Test Site (NTS) source scaling laws to those at other sites. The Joint Verification Experiment (JVE) indicates that a magnitude (mb) bias (δmb) exists between the Semipalatinsk test site (STS) in the former Soviet Union (FSU) and the Nevada test site (NTS) in the United States. Generally this δmb is attributed to differential attenuation in the upper-mantle beneath the two test sites. This assumption results in rather large estimates of yield for large mb tunnel shots at Novaya Zemlya. A re-examination of the US testing experiments suggests that this δmb bias can partly be explained by anomalous NTS (Pahute) source characteristics. This interpretation is based on the modeling of US events at a number of test sites. Using a modified Haskell source description, we investigated the influence of the source Reduced Displacement Potential (RDP) parameters ψ ∞ , K and B by fitting short- and long-period data simultaneously, including the near-field body and surface waves. In general

  4. Seismic vulnerability and damage of Italian historical centres: A case study in the Campania region

    Science.gov (United States)

    Formisano, Antonio; Chieffo, Nicola; Fabbrocino, Francesco; Landolfo, Raffaele

    2017-07-01

    The preservation of masonry buildings typical of Italian historical centres represents a very pressing dilemma founded on recovery need of the urban fabric original character. In the paper, based on a methodology developed by some of the Authors on building aggregates, the seismic vulnerability estimation of some masonry compounds in the heart of the town of San PotitoSannitico (Caserta, Italy) is presented and compared to the results achieved from applying the basic literature method for isolated constructions. Finally, the damage scenario of inspected buildings has been shown by highlighting clearly the influence of different positions of structural units on the damages that masonry aggregates suffer under different grade earthquakes, leading to individuate the most vulnerable buildings.

  5. Seismic Travel Time Tomography in Modeling Low Velocity Anomalies between the Boreholes

    Science.gov (United States)

    Octova, A.; Sule, R.

    2018-04-01

    Travel time cross-hole seismic tomography is applied to describing the structure of the subsurface. The sources are placed at one borehole and some receivers are placed in the others. First arrival travel time data that received by each receiver is used as the input data in seismic tomography method. This research is devided into three steps. The first step is reconstructing the synthetic model based on field parameters. Field parameters are divided into 24 receivers and 45 receivers. The second step is applying inversion process for the field data that consists of five pairs bore holes. The last step is testing quality of tomogram with resolution test. Data processing using FAST software produces an explicit shape and resemble the initial model reconstruction of synthetic model with 45 receivers. The tomography processing in field data indicates cavities in several place between the bore holes. Cavities are identified on BH2A-BH1, BH4A-BH2A and BH4A-BH5 with elongated and rounded structure. In resolution tests using a checker-board, anomalies still can be identified up to 2 meter x 2 meter size. Travel time cross-hole seismic tomography analysis proves this mothod is very good to describing subsurface structure and boundary layer. Size and anomalies position can be recognized and interpreted easily.

  6. Depth geological model building: application to the 3D high resolution 'ANDRA' seismic block

    International Nuclear Information System (INIS)

    Mari, J.L.; Yven, B.

    2012-01-01

    Document available in extended abstract form only. 3D seismic blocks and logging data, mainly acoustic and density logs, are often used for geological model building in time. The geological model must be then converted from time to depth. Geostatistical approach for time-to-depth conversion of seismic horizons is often used in many geo-modelling projects. From a geostatistical point of view, the time-to-depth conversion of seismic horizons is a classical estimation problem involving one or more secondary variables. Bayesian approach [1] provides an excellent estimator which is more general than the traditional kriging with external drift(s) and fits very well to the needs for time-to-depth conversion of seismic horizons. The time-to-depth conversion of the selected seismic horizons is used to compute a time-to-depth conversion model at the time sampling rate (1 ms). The 3D depth conversion model allows the computation of an interval velocity block which is compared with the acoustic impedance block to estimate a density block as QC. Non realistic density values are edited and the interval velocity block as well as the depth conversion model is updated. The proposed procedure has been applied on a 3D data set. The dataset comes from a High Resolution 3D seismic survey recorded in France at the boundary of the Meuse and Haute-Marne departments in the vicinity of the Andra Center (National radioactive waste management Agency). The 3D design is a cross spread. The active spread is composed of 12 receiver lines with 120 stations each. The source lines are perpendicular to the receiver lines. The receiver and source line spacings are respectively 80 m and 120 m. The receiver and source point spacings are 20 m. The source is a Vibroseis source generating a signal in the 14 - 140 Hz frequency bandwidth.. The bin size is 10 x 10 m 2 . The nominal fold is 60. A conventional seismic sequence was applied to the data set. It includes amplitude recovery, deconvolution and wave

  7. Seismic Studies

    Energy Technology Data Exchange (ETDEWEB)

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground

  8. Seismic Studies

    International Nuclear Information System (INIS)

    R. Quittmeyer

    2006-01-01

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

  9. Tourism sector preparedness in zones with a high seismic risk: Case study of the Capital Region of Japan

    Science.gov (United States)

    Lihui, W.; Wang, D.

    2017-12-01

    Japan is a country highly vulnerable to natural disasters, especially earthquakes. Tourism, as a strategic industry in Japan, is especially vulnerable to destructive earthquake disasters owing to the characteristics of vulnerability, sensitivity and substitutability. Here we aim to provide theoretical understanding of the perception and responses of tourism managers towards damaging disasters in tourism destinations with high seismic risks. We conducted surveys among the mangers of tourism businesses in the capital area of Japan in 2014 and applied structural equation modeling techniques to empirically test the proposed model with four latent variables, which are risk perception, threat knowledge, disaster preparedness and earthquake preparedness. Our results show that threat knowledge affects risk perception and disaster preparedness positively. In addition, disaster preparedness positively affects earthquake preparedness. However, the proposed paths from risk perception to disaster preparedness, risk perception to earthquake preparedness, and threat knowledge to earthquake preparedness were not statistically significant. Our results may provide references for policymakers in promoting crisis planning in tourism destination with high seismic risks.

  10. Seismic Response Analysis and Test of 1/8 Scale Model for a Spent Fuel Storage Cask

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Han; Park, C. G.; Koo, G. H.; Seo, G. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Yeom, S. H. [Chungnam Univ., Daejeon (Korea, Republic of); Choi, B. I.; Cho, Y. D. [Korea Hydro and Nuclear Power Co. Ltd., Daejeon (Korea, Republic of)

    2005-07-15

    The seismic response tests of a spent fuel dry storage cask model of 1/8 scale are performed for an typical 1940 El-centro and Kobe earthquakes. This report firstly focuses on the data generation by seismic response tests of a free standing storage cask model to check the overturing possibility of a storage cask and the slipping displacement on concrete slab bed. The variations in seismic load magnitude and cask/bed interface friction are considered in tests. The test results show that the model gives an overturning response for an extreme condition only. A FEM model is built for the test model of 1/8 scale spent fuel dry storage cask using available 3D contact conditions in ABAQUS/Explicit. Input load for this analysis is El-centro earthquake, and the friction coefficients are obtained from the test result. Penalty and kinematic contact methods of ABAQUS are used for a mechanical contact formulation. The analysis methods was verified with the rocking angle obtained by seismic response tests. The kinematic contact method with an adequate normal contact stiffness showed a good agreement with tests. Based on the established analysis method for 1/8 scale model, the seismic response analyses of a full scale model are performed for design and beyond design seismic loads.

  11. Seismic testing

    International Nuclear Information System (INIS)

    Sollogoub, Pierre

    2001-01-01

    This lecture deals with: qualification methods for seismic testing; objectives of seismic testing; seismic testing standards including examples; main content of standard; testing means; and some important elements of seismic testing

  12. Waveform modeling of the seismic response of a mid-ocean ridge axial melt sill

    Science.gov (United States)

    Xu, Min; Stephen, R. A.; Canales, J. Pablo

    2017-12-01

    Seismic reflections from axial magma lens (AML) are commonly observed along many mid-ocean ridges, and are thought to arise from the negative impedance contrast between a solid, high-speed lid and the underlying low-speed, molten or partially molten (mush) sill. The polarity of the AML reflection ( P AML P) at vertical incidence and the amplitude vs offset (AVO) behavior of the AML reflections (e.g., P AML P and S-converted P AML S waves) are often used as a diagnostic tool for the nature of the low-speed sill. Time-domain finite difference calculations for two-dimensional laterally homogeneous models show some scenarios make the interpretation of melt content from partial-offset stacks of P- and S-waves difficult. Laterally heterogeneous model calculations indicate diffractions from the edges of the finite-width AML reducing the amplitude of the AML reflections. Rough seafloor and/or a rough AML surface can also greatly reduce the amplitude of peg-leg multiples because of scattering and destructive interference. Mid-crustal seismic reflection events are observed in the three-dimensional multi-channel seismic dataset acquired over the RIDGE-2000 Integrated Study Site at East Pacific Rise (EPR, cruise MGL0812). Modeling indicates that the mid-crustal seismic reflection reflections are unlikely to arise from peg-leg multiples of the AML reflections, P-to- S converted phases, or scattering due to rough topography, but could probably arise from deeper multiple magma sills. Our results support the identification of Marjanović et al. (Nat Geosci 7(11):825-829, 2014) that a multi-level complex of melt lenses is present beneath the axis of the EPR.